part i. p. 133; _Dr. B. Jones' Anim. Chem._, pp. 20, 118.)

It is the general opinion of modern chemists, that before the starch of the food can be applied to the maintenance of the animal heat, for which office it is chiefly intended, it passes through a series of chemical changes. First, assuming two equivalents of water, it becomes grape-sugar; next, this changes into lactic acid, which is isomeric with it; and this again combines with twelve atoms of oxygen, to form carbonic acid and water. This last change is a process of combustion, and thus produces heat. The oxygen needed for it is absorbed from the air by the pulmonary mucous membrane, and the carbonic acid formed passes out of the blood at the same surface.

Liebig was the first to point out the connexion between these changes and the phenomena of Diabetes. It is clear that if the process were to stop at the formation of grape-sugar, the condition of blood that exists in Diabetes would result. This sugar cannot be put to any use, and is excreted as fast as formed. There is an excess of urea in the whole quantity of urine passed in the day; probably because the nitrogenous food and tissues are undergoing combustion instead of the starch. Before becoming grape-sugar, starch undergoes a transitional change into Dextrine, a gummy insipid substance which has the same composition as itself. It seems that the process may even stop as early as this, and that by this stoppage another analogous disease may be produced, _i.e._ Diabetes insipidus. The common Diabetes is called D. mellitus. (_Vide Jones' Anim. Chem._ p. 120.)

If it were clearly proved that the acid of Rheumatic fever is lactic acid, then this affection might evidently be produced by a stoppage of the process at the next stage. Lactic acid has been formed; but, for some reason unknown, it is not oxidized into carbonic acid. Urea and uric acid are in excess in the urine, from the cause alleged above.

But suppose some of the sugar to be oxidized prematurely, without passing first into lactic acid. By this oxalic acid would be produced, and the phenomena of Oxaluria accounted for.

These things are only alleged as possible, and for the purpose of showing that, should they be true, the action of some useful remedies might be elucidated. It is not at all unlikely that the accuracy of such ideas may be completely established by fresh discoveries at no distant time. But let us continue.

In Gout and Lithiasis there is an excess in the system of nitrogenous matter, and thus a tendency to an extra formation of urea. These conditions are often brought on, and always aggravated, by over-indulgence in animal food. Now if we may suppose that some of the lactic acid, instead of oxidizing directly into carbonic acid, oxidizes in combination with this urea which is in excess, then uric acid and water might result, as is shown below. The uric acid passes out into the urine in excessive quantity.

Should this be the case, the great affinity existing between the course and symptoms of Gout and Rheumatism would be easily explained, there being in both disorders an impediment to the proper oxidation of lactic into carbonic acid. These things may be illustrated by a diagram, showing the results which are supposed to take place when the natural process is arrested at, or diverted from, any of its stages:--

Starch. |+ |2 |a |q |= Grape Sugar (Diabetes.) | |\ | \ | \+ O = | \ | \ | \ Oxalic acid. (_Oxaluria._) | |= Lactic acid (Rheumatism.) | |\ | \ | \+ 2 Urea + O 6 = | \ Uric acid + 10 aq. (_Gout, and Lithiasis._) |+ |O |= Carbonic acid.

Thus, at each of the two transitional stages, we might have one diseased condition produced by an arrest of the process, and another by its deviation. These deviations and stoppages may result from a failure of some natural principle which is gifted with the control and direction of the series of transformations; or they may simply be traceable to a want of vital energy, or nervous force.

The same ideas may be more distinctly expressed by a few chemical equations.

_Natural process._ C_{12}H_{10}O_{10} + 2 HO = C_{12}H_{12}O_{12}. = 2 (C_{6}H_{5}O_{5}, HO.) C_{6}H_{6}O_{6} + O_{12} = 6 CO_{2} + 6 HO.

_Oxaluria._ C_{12}H_{12}O_{12} + O_{18} = 6 C_{2}O_{3} + 12 HO.

_Gout and Lithiasis._ Lactic acid + 2 Urea + O_{5} = Uric acid + 10 HO.

The last equation may be thus proved at length:--

C_{6} H_{6} O_{6}. C_{10}H_{4} O_{6} N_{4}. C_{4} H_{8} O_{4} N_{4}. O_{6}. H_{10}O_{10}. ------------------------ ------------------------ C_{10}H_{14}O_{16}N_{4}. = C_{10}H_{14}O_{16}N_{4}.

It is next to be inquired how far the theoretical explanation of these diseases which has thus been sketched out can be applicable to the matter in which we are more immediately interested, viz., the action of the Catalytic remedies used to cure them.

For the radical cure of Diabetes there is no known remedy; though some relief may be afforded by a system of dieting. (_Vide Aliments._) It is supposed that what we have to do is to convert diabetic sugar, _i.e._ grape-sugar, into lactic acid. This acid probably exists in the gastric juice. And some such substance as Pepsin, or the decomposing Caseine in sour milk, which is capable of effecting this change out of the body, might perhaps avail us, if we could contrive to introduce it into the blood.

In Oxaluria, the best treatment consists in a course of Nitro-hydrochloric acid. This remedy is prepared by adding one part of Nitric to two of Hydrochloric acid; and is diluted considerably with water when prescribed. The Nitric acid causes the oxidation of some of the Hydrogen of the other acid, and thus sets free Chlorine gas. This is stated by Mr. Brande to go on until the liquid is saturated with this gas. The result of the presence of Chlorine is, that from the affinity of this gas for Hydrogen, by which, under certain circumstances, it is enabled to set free the Oxygen of water, this compound acid becomes the most powerful oxidizing agent known. This acid has been lately used as a remedy for Gout and Rheumatism, in spite of the acid state of the fluids in those cases; and I believe it to be a very valuable medicine in both of these disorders. A simple mineral acid would do no harm in both instances. The Nitro-hydrochloric acid must operate in some special way.

It is probable that its action may depend upon its oxidizing power.

In Oxaluria it might cause the oxalic acid to be oxidized into carbonic acid, and thus restore health. Thus:

C_{2}O_{3}+O = 2 CO_{2}.

In Rheumatic fever, where we have supposed that lactic acid is formed as it should be, but then stops short, and proceeds no further, the oxidizing agent may convert this into carbonic acid.

In Gout and Lithiasis, where there seems to be an excess of nitrogen in the system, and thus more oxygen is needed to restore the equilibrium, I have supposed that lactic acid and urea are changed together into uric acid. If we adopt this hypothesis, it will be evident that under the above treatment this uric acid may be oxidized back into urea and carbonic acid, and the balance of health restored. Thus:

Uric acid + 6 O + 4 HO = 2 Urea + 6 CO_{2},

which may thus be proved:

C_{10}H_{4}N_{4} O_{6} O_{6} C_{4} H_{8}N_{4} O_{4}. H_{4} O_{4} C_{6} O_{12}. ---------------------- ----------------------- C_{10}H_{8}N_{4}O_{16} = C_{10}H_{8}N_{4}O_{16}.

Such may be the action of Nitro-hydrochloric acid. It exerts a true Catalytic or counteractive influence. But we have to explain the agency of another class of very different, and apparently opposite remedies. Alkalies are employed with benefit both in Rheumatism and in Gout; particularly in the former disease. Now I conceive these to act, in Rheumatism at least, simply on the Restorative principle; supposing lactic acid to exist in excess in Rheumatic blood. This by itself may have no more tendency to oxidize into carbonic acid, than so much vegetable acid would have. In ordinary cases a free vegetable acid passes out into the urine without undergoing any change in the system. But it has been proved by Wöhler that the same vegetable acid becomes oxidized when given in combination with an alkali. So that if we introduce into Rheumatic blood a free alkali, a lactate of potash or of soda will be formed; this may then be enabled to oxidize into a carbonate, and the natural process be completed. Such appears to be the rationale of the action of alkalies. They would be inefficacious in Oxaluria, because the oxalic acid has so great an affinity for lime, that it could not be separated from this combination by an alkali.

Dr. Rees and others have found Lemon juice of great use in the treatment of acute Rheumatism. It contains Citric acid, and some Citrate of Potash; the latter being in too small amount to explain the action of the remedy. I have already shown how it seems possible that the vegetable acids may act as refrigerants in simple fever; how they may then supply the place of the natural lactic acid in the blood, and become oxidized instead of the Proteinaceous compounds. (_Vide Acids._) But Rheumatic fever is a very different case, for there is here apparently an excess of lactic acid, and an arrest of its oxidation. In considering, however, the formula for Citric acid, we perceive that not only does it contain proportionally more Oxygen than Proteins, as was proved in the former instance, but more than lactic acid contains. It is

C_{12}H_{5}O_{11} + 3 HO.

Thus it is possible that it may act as a carrier of oxygen to the lactic acid, and so help it on towards its transformation into carbonic acid. It appears to be decomposed in the system, for Dr. Rees has never known it in these cases to increase the acidity of the urine. The matter is obscure; but we can discern enough of it to convince us of the possibility of different medicines acting in diverse ways so as to produce very similar results.

Colchicum has apparently some power in the diversion or control of these morbid processes, which we can only indicate, but cannot further comprehend. It is generally best to give it so that it shall neither produce purging, nor any great degree of general depression.

Mercury and other medicines which promote the secretion of the liver, are found to be of considerable use in the treatment of all of these diseases, but more especially in Gout. They seem to act by virtue of their power in eliminating and producing Bile. And it is likely that some constituent of Bile, reabsorbed into the blood, is able to exert a beneficial influence on the conduct of such processes as those which we have just now considered.

Quinine and Tonics have been strongly recommended by Dr. Todd in Gout; and they seem to be signally efficacious, both in this and in the other Arthritic disorders. This is a very interesting fact. If there should be any truth in an idea which I have explained at length in the article on Tonics (_vide_ p. 142,) it would seem that these Tonics may be of use by supplying in the blood the place of one of the wanting elements of Bile. For in all Arthritic disorders there is more or less of hepatic derangement.

There seem then to be six separate and distinct explanations of the cure of these Arthritic diseases. There are six different modes of operation by which the same beneficial result may follow the employment of Nitro-hydrochloric acid, free Alkalies, Lemon juice, Colchicum, Mercury and Quinine.

So that if it should be proved, which is not unlikely, that the chemical theory propounded above for the purpose of accounting for the production of these disorders in the blood is a correct view of the case, then this explanation of the action of the various remedies used in such diseases would acquire an additional probability. But at present the idea is purely hypothetical, because depending upon a number of things which, although they seem likely, are far from being proved as yet.

All that we can affirm with any degree of certainty is that a number of blood-medicines are applied with advantage to the treatment of these kindred disorders, tending to counteract the morbid conditions by which they are severally produced. These Antiarthritics must operate, then, on the Catalytic principle.

A number of varieties and masked forms of these disorders are grouped together under the general title of Dyspepsia. The depraved condition of the blood which tends to the production of arthritic symptoms may, when controlled and disturbed by various causes, simply manifest itself by causing acidity of the stomach, flatulence, impairment of digestive power, and general lassitude. Different Antiarthritic remedies are applicable in different cases. Colchicum or Nitro-hydrochloric acid are serviceable when this condition of the system is of long standing. Small doses of Mercury are often efficacious. Tonics, and a Purgative occasionally, may be recommended in milder forms of the disorder.

ORD. V. ANTISCORBUTICS.

These are remedies which are useful in the counteraction of Scurvy and Purpura. In these disorders there is a thin and poor condition of the blood, together with a deficiency in the amount of albumen, fibrine, and the solids generally; a tendency to hæmorrhages and ulcerations, consequent on this condition of the blood; and great general depression and debility.

There is no doubt that these changes in the blood are due to a certain morbid action. It seems that there are some kinds of food which are able to prevent the occurrence of this morbid action, or to control it when it has been set up. The worst forms of Scurvy occur among sailors in long voyages, who have been deprived for some time of fresh vegetable food; and it is often observed that those who have been thus afflicted on land have been subjected to the same deprivation.

But it does not follow as a matter of course that those who are thus deprived become invariably the victims of Scurvy. It seems that there are certain constitutions which are more disposed to it than others; and that when these systems are deprived of some articles of diet which are able to prevent or to neutralize the working of the poison in them, the latent morbid action is allowed to commence.

Of all the substances of which trial has been made, Lemon or Lime juice, and Potatoes, are said to be of the greatest use in the treatment of scurvy. The former is generally employed on board ships. These both contain Citric acid and salts of potash. But the chief agent in the cure should be something which is not contained in the food eaten by those who are commonly attacked with Scurvy. The food of the sailors who are thus afflicted consists mainly of salted beef and sea-biscuit. Both contain salts of Potash; neither contain Citric acid. So that from this consideration it would seem as if the free acid must be the remedial agent. Vegetables in their fresh state generally contain a small quantity of this or some other acid; and fresh vegetable food is always the best prophylactic against Scurvy and Purpuric diseases. Various wild herbs, some of which contain Oxalic instead of Citric acid, are used among the poor for this purpose.[41]

Dr. A. B. Garrod is of opinion that Scurvy is attributable to a deficiency in the system of the natural amount of the salts of Potash; he therefore treats it with salts of Potash, and apparently with success. (_Monthly Journal of Medicine_, January, 1848.)

The salts of Potash, if used on such grounds, would obviously act as Restorative agents, and supply to the blood a material in which it is deficient. But Citric acid could not remain in the blood; and if it cures Scurvy, it must act on the Catalytic principle. It could not supply to the system any permanent material.

Dr. Garrod concludes from analysis that the antiscorbutic articles of diet are distinguished by containing an abundance of the salts of Potash, but that the reverse is the case with the materials which form the staple food of those who are most liable to Scurvy.

He gives the following as the amounts of potash obtained from one ounce of each of the articles of diet named:--

Wheaten bread .259 grains. Oatmeal .054 " Salted beef .572 " Boiled potatoes .529 " Lemon-juice .846 "

Thus it appears that lemon-juice and potatoes contain more Potash than wheaten bread, and much more than oatmeal. But they do not so much excel salt beef in this particular, and that is one of the chief articles of diet among sailors. And if this deficiency of Potash were the sole cause of Scurvy, then it should be unknown in Ireland, where quantities of Potatoes are eaten, and very common in Scotland, where Oatmeal forms so important an article of diet among the peasantry. I am certainly not aware that such is the case, but believe it is rather the reverse.

In spite of the very able arguments and the instances adduced on the other side, it seems to me that the probability is still in favour of the vegetable acid being the active or curative agent in these antiscorbutic vegetables. It seems to exert a purifying power over the blood in this disorder, of the exact nature of which we are not aware. It is probably not only Citric acid that is efficacious, for it appears that some other vegetable acids, and vegetables which do not contain Citric acid at all, may be used with advantage in Scorbutic diseases.

ORD. VI. ANTIPERIODICS.

Certain mineral medicines of the Catalytic division are employed in the treatment of periodic disorders.

Arsenic is a medicine of considerable power, which, when given in too large a dose, or indeed when given at all in most cases, becomes a poison. It has already been shown to act in the blood, and to produce in it a number of effects of a particular kind. One part of this operation is that it is capable of antagonizing the poisons of intermittent disorders, as also of certain convulsive affections and skin-diseases. In health a poison, in disease it proves a remedy. But the dangerous nature of its action is such as to demand considerable care in the administration of the preparations of Arsenious acid.

Dr. A. T. Thomson states that the action of Arsenic is liable to exacerbations and remissions, and sometimes even intermissions. Thus we may suppose that there is a certain degree of analogy between its operation and that of the malarious poison, by virtue of which it may perhaps exert a corrective power over the working of the latter in the blood. (_Vide_ page 166.) Such an analogy could only exist in the case of a Catalytic medicine. It is not observed of Quina, which is employed in intermittents on the Restorative plan. Arsenic is foreign to the blood, and is in every way a Catalytic medicine.

In large doses Arsenical preparations act on the stomach as irritant poisons. Some of them have been used externally as Caustics, especially in Lupus. But this is a kind of action that does not concern us now.

The officinal solution of Arsenite of Potash was introduced into notice by Dr. Fowler, and is the chief preparation of Arsenic employed. De Valangin's solution contains a Terchloride of Arsenic, and is of less than half the strength of the others. Both of them are used in Ague. Some recommend, in all cases where Arsenic is used, to begin with small doses, as two drops of Fowler's solution three times a day, and gradually to increase the quantity; from the idea that the system will thus be enabled to tolerate the remedy better, and that irritation of the stomach will be avoided. Mr. Hunt deprecates this practice, and recommends regular doses of three to five drops or more. It may be safely continued during the paroxysm of Ague, which is a plan that is generally considered to be unadvisable in the case of Quina. The latter may be given in a very full dose between the paroxysms; but this cannot be done with Arsenic, for the consequences would be dangerous. It is best in all cases to give the Arsenic after a meal, on a full stomach, as then it is less likely to irritate, not coming directly in contact with the coats of the stomach, and being diluted by the food during its absorption.

Arsenic is useful in other intermittent disorders besides Ague, as in the various kinds of intermittent neuralgia. It has been given in some varieties of intermittent pulse, which are not due to organic disease of the heart. Dr. Darwin cured a case in which the beats of the heart intermitted regularly once in every three or four times, by the administration of four drops of a saturated solution of Arsenious acid three times a day.

The preparations of Arsenic have even been used in some cases of Gastrodynia with considerable advantage. In these instances the disorder of the stomach generally assumes an intermittent form. It has been supposed by some that Arsenic in such disorders acts directly upon the nerves; but it appears to counteract all the manifestations of this intermittent poison, whether local or general, by the same action in the blood. (_Vide_ page 212.)

Several attempts have been made at different times to discover a substitute for Arsenic, and a cheaper remedy than Quinine, for the treatment of Ague. Iron is employed with advantage in old chronic cases attended with Anæmia; but it is not of service by counteracting the intermittent, but by remedying the anæmic condition which co-exists with it.

M. Piorry, in the course of some experiments made at the Hôpital de la Pitié at Paris, has found common salt in half-ounce doses to be very efficient. In his opinion it is more efficacious than Arsenic, and second only to Quinine, in the cure of this disorder. The suggestion is a valuable one; but the dose is very bulky, and it would be difficult to prevent it from causing vomiting in many cases.

Alum is another medicine which has been recommended in Ague. It also appears to act on the Catalytic plan; but it has not been often employed.

The compounds of Arsenic are found to exert a curious antiseptic influence on dead animal tissues. They particularly prevent decomposition in animal membranes, by virtue of a combination which Arsenic forms with Gelatine. Liebig has founded on these facts a theory of the medicinal action of Arsenic. (_Anim. Chem._, part i. p. 206.) He supposes that substances as Arsenic and Mercury may be able to arrest contagious and other disorders in the system in the same way that they control putrefaction out of the body. The use of Salt and Alum in Ague might seem at first sight to countenance such a hypothesis as applicable to the treatment of this disease. But we know that Arsenic does not stop all fermentations. The grain of wheat will germinate, and its starch be converted into sugar, after it has been steeped in a solution of Arsenic to protect it from vermin. And Gelatine, for which Arsenic has an affinity, has not been proved to exist in healthy blood.

The compounds of Mercury, the operation of which in Syphilis is sought to be explained on these grounds, are not nearly so antiseptic as many other minerals. If this theory were correct, then all Catalytic medicines, and all antiseptic substances, should be of equal efficacy in all morbid processes. But this is far from being the case. Many substances which are distinguished for their antiseptic powers are found to have no influence whatever on the progress of these disorders. Are Acetic acid and Creosote of any use in Ague? Does Alcohol prevent the drunkard from contracting Syphilis? And if Arsenic, Alum, and common salt, acted solely by arresting fermentation, how is it that they have no control over the supposed fermentations of Syphilis and other diseases? The explanation required must needs be more specific and particular.

ORD. VII. ANTICONVULSIVES.

I have already sought to show that the metallic substances which are used in the treatment of spasmodic disorders act in the blood, and tend to establish in it a set of actions of a peculiar kind. I am able to add little respecting the rationale of their action to that which I have said of the operation of Catalytic medicines in general. It is certainly very mysterious; and it is perhaps mainly on this account that some have been induced altogether to deny it. But a denial so grounded is disingenuous and wrong, for we must often be content to know and to receive many things that we do not understand.

Perhaps the most evident and characteristic of these agencies is that of Nitrate of Silver in the cure of Epilepsy. The Acetate of Lead, and the Ammonio-sulphate of Copper, have been used with advantage in the same disorder. Dr. Babington strongly recommends the Sulphate of Zinc, given at first in small doses, and then gradually increased, so that it may not produce vomiting.

In the treatment of Chorea, Arsenic is highly esteemed and recommended by Dr. Pereira.

In Hysteria these medicines are all probably more or less applicable; but on account of the obstinate and multiform nature of this disease, their use in it is less obvious than in Epilepsy and Chorea. Hysteria, too, is more under the influence of Nerve-medicines than are the other two diseases.

The great objection to Silver, in whatever form given, is that its salts are liable to be reduced in the system, and it thus tends to produce a permanent discoloration of the skin, either browning it or communicating to it a dull leaden hue. This naturally constitutes a strong ground of objection with the unfortunate patient, who would often prefer to be left alone with his fits than to be turned blue for life.

M. Georget supposes that the advocates for the use of Nitrate of Silver in Epilepsy employ it on the principle of counter-irritation, saying that they attempt to cure a diseased brain by cauterizing the stomach. (_Physiology of the Nerv. System_, vol. ii. p. 401.) But I am not aware that any English therapeutists have adopted this view of its mode of operation. The dose of the Nitrate of Silver, and the state of dilution in which it is given, would certainly prevent it from manifesting any such action. And we should not be warranted in supposing that any of the medicines of this or any other order of Catalytic remedies could act in so direct and so easy a way as that, even if it were thus possible.

Some have supposed that Nitrate of Silver cures Epilepsy by diminishing an irritable condition of the stomach. But it is observed by Dr. Pereira that the existence of this irritability in all cases of Epilepsy is a mere assumption. The solution of this salt exerts, according to its strength, an astringent or caustic action on all mucous surfaces, and thus improves their condition when they are relaxed, inflamed, irritable, or ulcerated. The occasional benefit which follows the administration of the preparations of Silver in Gastrodynia may be referred to an action of this kind. The action of Arsenic in some intermittent varieties of this painful affection has already been mentioned, and is explained in another way. Caustic substances probably act locally in these cases; but Arsenious preparations exert an Antiperiodic influence in the blood generally.

Tetanus is by far the most incurable of these convulsive disorders. Arsenic and other medicines of this order have been recommended in the treatment; but although some cases appear to be partly connected in their first origin with a certain condition of the blood, this disease is very little under the influence of blood medicines, or indeed of any medicines at all.

ORD. VIII. ANTISQUAMICS.

Skin diseases are both caused and cured in a variety of ways. Some are produced by external influences. They may be brought on by mere irritation, as certain kinds of Eczema and Herpes, and are then to be treated with soothing unguents or cool lotions. Or they may even be connected with some external organization, of a vegetable or animal kind, as Porrigo and Favus are traceable to a parasitic fungus, and Scabies is accompanied by the development of a species of Acarus. Others are due to some wrong in the digestive process, or to a plethoric condition of the system. Urticaria is an example of the former, Acne of the latter. They may generally be treated most effectually by the exhibition of salines and rhubarb.

A third class of skin diseases are due to the existence in the blood of certain poisons or peculiar morbid conditions. The eruption may constitute one only among many symptoms of the action of this poison, or it may be the chief or only symptom. The former is the case in Syphilis and the Eruptive fevers. It is with the latter kind that we are now concerned.

There are two modes by which we may get rid of the poison that causes the eruption--Elimination and Counteraction. The first may sometimes be effected by the use of Purgatives, Sudorifics, or Diuretics.

But I have classed in this last order of Catalytic blood-medicines some remedies that have proved useful in counteracting the causes of these diseases. The eruptive disorders alluded to are all connected together both in their symptoms and treatment; but because the squamous diseases, Lepra and Psoriasis, are the most characteristically under the influence of these remedies, the latter have been named Antisquamics.

Arsenious acid, as contained in Fowler's solution, a remedy already twice named among Catalytics, is also the most powerful of these Antisquamic agents. Mr. Hunt considers it to be a specific for all skin diseases that are not syphilitic in their origin. Besides Lepra and Psoriasis, it is found useful in Eczema, Impetigo, and Lupus. In the last disorder it has been used both externally and internally, seeming to be in both cases specific in its action. Thus we find in these skin diseases another special antagonism for this extraordinary medicine, which has already been shown to be of considerable efficacy both in periodic and convulsive disorders.

Pitch or Tar is another remedy which seems to be capable of counteracting the scaly disorders. It may be either applied externally, or given internally in doses of 10 to 20 grains. It has been recommended for employment in some of the other skin diseases, but its advantage in them is not so obvious. When it is applied to the skin, some one of its principles is probably absorbed. Pitch, as a remedy for Lepra, is comparatively of recent introduction, but its efficacy has already been very widely acknowledged.

Tincture of Cantharides and Acetate of Potash, both diuretics, have been employed in Lepra to eliminate the _materies morbi_ from the blood into the urine, and have sometimes appeared to succeed in so doing. But in this, as in many other cases, counteraction is both easier and more certain than elimination. The system itself naturally attempts this elimination, and when it finds it impossible, we often gain nothing by urging it.

I need scarcely say that these remedies are applicable only in simple Lepra and Psoriasis, and not in the syphilitic forms of those eruptions, which are treated best by Mercury, or by other medicines of the second order of Catalytics. These Syphilitic eruptions are distinguished by a coppery or a livid-grayish colour, and by the absence of itching.

Sulphur has been used with benefit in Eczema, Impetigo, and Lepra. It may be administered externally in the form of fumigation or ointment, or internally in combination with an alkali or with Iodine. In the case of Eczema and Impetigo, the fumigation and internal administration are preferable, as the ointment is apt to increase the existing irritation. In the cure of Lepra the mineral waters of Harrowgate and other places, containing Sulphuretted Hydrogen gas, have been much recommended. Thus we have in Sulphur a third Antisquamic medicine. It is more or less useful in all non-syphilitic cutaneous disorders. Dr. Burgess has found sulphur ointment and fumigations to be very useful in Psoriasis palmaris. (_On Eruptions of the Face, etc., p._ 229.)

Though Sulphur seems to act specifically in the treatment of these disorders, there is another disease of a similar kind which it has been supposed to cure by a mere external agency. This is Scabies. Some have fancied that even here it acted specifically, and that this also was a blood-disease. But Scabies has long been attributed to an external cause, an insect, or, more correctly, an arachnid, which, by burrowing in the skin, is thought to produce the vesicular eruption. The Acarus Scabiei, or Itch insect, was discovered in 1179 by Abenzoar, the Arabian. In 1687 Dr. Giovanni Bonomo wrote a full account of it in a letter to Redi of Florence. It is supposed that Sulphur ointments and Sulphur fumigations have a direct external action in causing the death of this Acarus, by the bodily transmission of which from one person to another the contagious nature of the disease is accounted for.

Dr. Billing considers that the confirmation of this discovery has given the death-blow to an idea which will probably last as long as medicine; viz., that certain remedies exert a special influence in the cure of particular diseases. (_Principles of Medicine_, p. 75.) But we must not deny the existence of special agents, simply because we cannot understand their operation; for it is apparent in too many instances. And from the circumstance that Sulphur has proved beneficial when given internally in Scabies, as well as the fact that this disease has often an idiopathic origin, I am still disposed to doubt the value of the inference which is drawn from the discovery of the Acarus, and inclined to believe that Sulphur may exert an action of a specific kind in this disease as well as in the others.

Some other internal remedies, and many other external applications, have been used in Skin diseases; but these that I have mentioned are the only ones that appear to exert something of a special action in all cases. Arsenic is perhaps the most universal in its application. It often happens that when this remedy entirely fails, the eruption is connected with a constitutional taint of Syphilis. When there is a suspicion of this, such a remedy as Donovan's solution, containing both Arsenic and Mercury, is peculiarly applicable, because capable of acting in a double way. This medicine also contains Iodine; and either this preparation, or the Iodide of Potassium, should be prescribed when the skin disease appears to be connected with a strumous diathesis.

As soon as the course of Arsenic is found to produce swelling of the face, or irritation of the conjunctivæ, symptoms which denote the saturation of the system with the remedy, its administration should be suspended for a while.

We have now concluded the subject of Hæmatic medicines. I have said that this class has been very generally neglected and overlooked by writers on the subject. For this reason, and because there are some ideas respecting their action which I have thought it worth while to work out and to investigate at some length, I have devoted more space to its elaboration than I shall be able to spare for either of the remaining classes, in the consideration of which we are not likely to encounter so many interesting and debateable points.

PROP. VIII.--_That a second class of medicines, called_ NEUROTICS, _act by passing from the blood to the nerves or nerve-centres, which they influence._

1. _That of these, some, called_ STIMULANTS, _act so as to exalt nervous force in general or in particular._

2. _That others, called_ NARCOTICS, _act so as first to exalt nervous force, and then to depress it; and have also a special influence on the intellectual part of the brain._

3. _That others again, called_ SEDATIVES, _act so as to depress nervous force, in general or in particular._

Having investigated at some length the action of Blood-medicines, we now commence the consideration of another class of remedies, which differ very widely from the last in their mode of operation.

The action of Hæmatics is slow, but more or less durable, because it is evidenced in the blood; and a change in the blood produced by this action continues for a longer or a shorter time.

The action of Neurotics, or Nerve-medicines, is rapid; but it is transient, and is soon over. A Neurotic medicine does not cause any change in the blood; and it cannot remain in it, but soon passes out. It acts by contact with nerve, apparently producing no lasting change even in nerve-fibre; and as the cause of the action cannot remain, the effect also soon passes away. Whereas Hæmatics, durable agents in the blood, are used to counteract the causes of inveterate and chronic disorders; these Neurotics, which produce a transitory, but more or less forcible impression on the nervous system, are employed to rouse it when torpid, or to depress it when over-excited. Rarely of use in chronic blood-disorders, they are given mostly in the temporary emergencies of acute diseases. But it is obvious that even a temporary agent may prove of permanent efficacy by remedying a temporary emergency.

It was feasible to attempt some explanation of the actions of medicines in the blood, occasionally more or less analogous to known chemical influences. But the agency of nerve-medicines is of a far more incomprehensible kind. When we consider that little or nothing is known, or can be known, about the ultimate causes of sensation, or motion, or nervous excitement, there is no need for wonder that we find ourselves at a loss to explain the operation of medicines that influence these conditions.

Thus I must chiefly limit my remarks on Neurotics to defining _what_ their action is, finding it impossible to state with certainty _how_ they act. And the field of inquiry being so limited, it follows that there is much less to be said about them than had to be said of Hæmatics.

Nearly all the powerful poisons that act after passage into the blood, belong to this class. Their action in most points of view is such as completely to exceed our means of comprehension.

Sudden death may be produced by it. But there is no apparent cause for this. We find no erosion or perforation of the coats of the stomach or intestines; no mechanical disorganization of the tissues, or chemical change in them; no hæmorrhage, or vascular disease; no rupture of nerve-fibres. Whence, then, could death have arisen? How could the mere presence of a few atoms in the blood,--half a grain, one-twentieth, or even one-fiftieth of a grain--how could this apparently contemptible influence have produced so essential a derangement of the vital functions as to stop them altogether? It is impossible to answer.

The action of such remedies in the sudden causation or alleviation of nervous symptoms, when applied in the cure of disease, is equally wonderful. How are we to account for their different actions on different nerves? How is it that Opium contracts the pupil, and Belladonna dilates it?--that Digitalis affects the heart, and Stramonium the respiration?--that Prussic acid will cause convulsions, and Hyoscyamus delirium? In what way are these various operations brought to pass? It is impossible to answer.

Though it is, I say, quite impossible to frame for any one of these questions a certain or satisfactory reply, on account of the manifest insufficiency of our acquaintance with the details of such actions as these, yet I must now venture to repeat an idea which I have already referred to at the commencement of this Essay (p. 46,) and state my belief in the bare possibility of the operations of Neurotic agents being explicable upon mechanical grounds. It is generally believed among scientific men that each particle of a compound body is made up of a number of indivisible atoms, each of which is inconceivably minute in size. And as these compound bodies have each a peculiar chemical constitution, so must each of their ultimate parts be composed of a peculiar arrangement of simpler atoms, and thus have a certain shape of its own more or less different from the shape of every other compound atom. Both the substance of a nerve, and the active part of a nerve-medicine, consist of a number of definite compound atoms. And it is possible that the atom of a stimulant medicine may be of such a shape as that it shall be unable to coincide with, or to fit into, the series of atoms forming the sensitive surface of the nerve, and thus irritate this when brought into contact with it; and that the compound atoms of a sedative may so arrange with these nerve particles as to fit among and extinguish their salient points, and annihilate their natural sensibility. We learn from the phenomena of the senses that the nerves are very much under the influence of mechanical impulses of all kinds, and particularly minute and inappreciable impulses of this description. Another fact which gives additional credibility to such an idea is, that those Neurotic substances which are chemically alike are in general alike also in their influence on nerve.

The particular way in which nerve-medicines affect different parts of the nervous system might perhaps be explained by supposing minute chemical differences in the composition of the atoms of which those parts are constructed, sufficient to alter their relations to the atoms of certain remedies. If we adopt the Atomic theory, we must perceive that no two chemical bodies can be precisely alike in the shapes of their particles. This various dissimilarity might throw some light upon the many shades of distinction between the operations of Neurotic medicines on different parts. Thus, as a general rule, both Morphia and Atropia are paralyzers of motor nerves. But they do not act alike on the Ciliary nerves by which the motions of the Iris are controlled. We may suppose that there is a certain chemical peculiarity in the particles of these nerves, by which they are enabled to coincide with the atoms of Atropia, and are thus blunted and paralyzed by them; but are, on the contrary, stimulated and excited by the atoms of Morphia, which have the contrary action, because unable, on account of their relative shape, to dove-tail with these atoms.

This idea is, as I have said, purely conjectural and fictitious, and is indeed likely to remain so; for the thing is not by its nature susceptible of proof, nor is it even possible to inquire into it. And I have only thought it worth while to explain it at length because it is desirable that every statement which is made, however improbable and unworthy of credence it may seem, should at least be placed in as clear a light as possible.

The action of a Neurotic is readily distinguished from that of Hæmatic medicines by the fact of its exerting a rapid and well marked influence of some kind on the nervous system. As it is impossible that the medicines contained in this class should remain in the blood, they therefore pass out of the blood through the glands, and in so doing generally act as Eliminatives. This, their secondary action, will be subsequently considered. It is generally of less importance than their action on nerve; with the exception of some which, as volatile oils and resins, exert a very feeble Neurotic action, but are comparatively powerful as Eliminatives. In this case the secondary action becomes the more important of the two.

The most dangerous symptoms of disease are evidenced in the nervous system. Neurotics are employed to control these symptoms as they arise, but Hæmatics are used to combat the cause of the disorder. As to their relative efficacy, there is an advantage and a disadvantage on each side. On the one hand, nerve-medicines are more numerous and more powerful than blood-medicines, and thus in the control of symptoms they are wielded with more immediate certainty than the others in the counteraction of diseases. On the other hand, the symptom that is dreaded is only relieved for a time by the Neurotic remedy, while the morbid condition that caused it continues, and will perhaps cause it again; but when a disorder is remedied by the employment of Hæmatic medicines, it is more or less permanently cured and put an end to.

In the above Proposition I have endeavoured to state as much as we know with certainty of the action of Neurotics. To this certainty I have already ventured to add a surmise, on which no certain reliance can be placed. But even if the theory of the action by atomic shapes should be rejected as improbable, because affording too easy an explanation of a naturally inscrutable operation, it would still seem likely that these medicines may take effect by exerting some minute and imperceptible influence on nerve-fibre, or producing in it some inappreciable disorganization or change, which has the effect of altering the natural performance of its functions. The effect of mechanical concussion or shock, which may produce death by minutely disarranging the particles of the nervous centres, presents an obvious analogy to the sudden and remarkable action of some nerve-poisons.

Having offered these vague suggestions as to the ultimate _modus operandi_ of Neurotics, I will now proceed to divide the Proposition in which their more obvious action has been stated into a number of minor propositions. These apply to the whole class. The three divisions will be afterwards shortly considered separately.

_m. p. 1._--That Neurotics are medicines which pass into the blood.

_m. p. 2._--That their action is evidenced by a change in one or more of those functions which are attributed to the nervous system.

_m. p. 3._--That it is necessary that they should pass from the blood to that part of the nervous system which is influenced by them.

_m. p. 4._--That they are of use in an over-excited or depressed state of the nervous system.

_m. p. 5._--That they are transitory in action, and cannot remain in the blood.

Some space and labour was required in the proof of the minor propositions relating to Hæmatics, for among them were included some things that are not universally acknowledged; but the above account of the action of Neurotics concerns matters that are very generally admitted, and will not occupy us nearly so long in its discussion.

In the first place it is affirmed that Neurotic medicines pass into the blood. In the consideration of Prop. II., it was shown that all of them,--whether vegetable alkaloids, volatile oils, resins, or mineral substances,--were more or less capable of being absorbed. That they do pass into the blood is proved by the fact that many of them have been detected there, as well as found in the secretions into which they must have entered from the blood. Ammonia, Hydrocyanic acid, Antimony, Assaf[oe]tida, Turpentine, Alcohol, and Camphor,--all of which are Neurotic agents,--have been chemically detected in the blood by Tiedemann and Gmelin. A still larger number have been discovered in the urine by Wöhler, particularly of volatile oils and odorous principles. The active principles of Opium, Belladonna, Stramonium, and Henbane, have been detected in the same secretion by others.

Thus Neurotics pass into the blood. That they act after this absorption, and not by contact with the mucous surface, was proved in the consideration of Prop. I.

The second minor proposition is borne out even by the names by which the recognised action of these medicines is distinguished. Considered as a class, they have no action on the blood, but their influence is quickly and obviously exerted on the nervous system, or on the vital functions which are universally attributed to that part of the animal frame. Stimulants are so called because they are found by experience to exalt nervous force; Sedatives, because they depress it. Thus Ammonia is given to prevent Syncope, caused by a weakness or failure in power of the nerves of the heart; and Aconite is prescribed to relieve pain caused by an over-excitement of the sensory nerves. Though in these examples Ammonia acts on the centre, and Aconite on the peripheral nerves, yet they are both capable of exalting or of depressing nervous force in general. But neither Stimulants nor Sedatives, as defined by me, exert any marked influence on the intellectual part of the brain. They do not affect the phenomena of mind, or of the four special senses which are immediately associated with it. This influence is confined to the intermediate division of Nerve-medicines, called Narcotics. Their general action is evidenced by a short or long primary stimulation,--and a subsequent depression of nervous force, which is also of variable intensity. At the same time they affect the mind in various ways; exciting it, confusing it or lulling it. Opium and Alcohol are examples of Narcotics. These distinctions are in most cases obvious and well defined.[42]

The third minor proposition repeats the rule of local access, which has already been enforced in treating of the fifth proposition. It was not necessary to maintain this in the case of medicines acting on the blood; but Neurotic agents must be shown to operate locally on the various nervous organs. I have only to repeat the arguments which were urged before. It is proved that the action of nerve-medicines cannot be propagated by nervous connexion, but that passage in the circulation is necessary; that the course of the latter is sufficiently rapid to account even for the action of Hydrocyanic acid; and that, however near a medicine be introduced to a nervous organ, it does not affect it unless it be allowed to reach it. The nerves are not naturally constituted for the conduction of medicinal impressions, but only for the passage of impulses of volition, sensation, or emotion. And this evidently forms a powerful safeguard to the system against the effects of a poison. The assertion is further maintained by the fact that the action of a Neurotic, when applied topically to the part which it tends to influence, is the same as that which is exerted by it on the same part after absorption. And lastly, some nerve-medicines have actually been found after death in the substance of those nerves and centres which had been affected by them during life.

The use of these medicines in the treatment of disease is defined in the fourth minor proposition. They have no influence in the blood. They are not employed in slow or long continuing diseases. Their applications depend on their known physiological tendencies, already stated. Abnormal deviations from the proper functions of the nervous system are rectified by means of the influence which they exert over the nervous organs.

When the powers of life are sinking, the nervous force on which life depends may perhaps be roused by a strong Stimulant, and maintained by its repetition. Sometimes the emergency may be thus postponed, and the danger escaped.

In violent inflammations and fevers, when the action of the heart is so violent, and the nerves that control it so excited, as to place life in peril, we may do good by the administration of a Sedative, such as Antimony or Digitalis, by which the nervous force may be reduced to its proper level.

Narcotics are used in various cases, to cause sleep, or to quiet mental irritability. Both these and Sedatives are employed to alleviate the different kinds of pain.

Neurotics are thus applied to various symptoms, and to many disorders. Their different modes of action will be detailed more at length presently. It must be remembered that all these actions, powerful though they may be, are transitory. The effect produced on the nerve is not a lasting one, and no essential change in the blood is effected by true Neurotics. They are not natural elements of this fluid, but must quickly pass out of it; and they having thus left it, their action also is over. Thus the truth of the fifth minor proposition is plain.

I will now attempt to give a brief but distinct account of the three divisions into which I have divided this class of medicines.

STIMULANTS.

Stimulants are medicines which pass from the blood to the nerves or nerve-centres, and act on them so as to exalt nervous force, in general or in particular. That is, they may extend their operation more or less to the whole nervous system, having a general tendency to communicate nervous energy; or they may confine their action to particular departments of this system, having no manifest influence on other parts. On referring to the arrangement at the commencement of the Essay, it will be seen that Stimulants are subdivided, according to whether their action is thus extended or confined.

STIMULANTIA.

Ord. 1. Stimulantia generalia. Ord. 2. Stimulantia specifica.

The first order includes all the medicines that are commonly understood to be Stimulants. But as the remedies of the second order obviously exalt nervous force, the term applied to the others on that ground could not consistently be withheld from them, although their action is more limited and local in its nature, being confined to a certain part of the body, and to certain nerves. The same remark may be made of the order of Special Sedatives, which will soon have to be considered.

ORD. I. GENERAL STIMULANTS.

(_Mineral substances._--Ammonia and its Carbonates. Phosphorus.

_Animal substances._--Musk, and Castor.

_Vegetables containing volatile oils._--The aromatic Labiatæ, Compositæ, and Umbelliferæ. Cloves and Nutmeg. Cinnamon, Cassia, Sassafras. Rue, Barosma. The Aurantiaceæ. Canella. Valerian. Mustard. Cajeput and Pimenta. Hops. Juniper, Turpentine. Cardamom. Onion.

_Vegetables containing acrid principles._--Senega. Horseradish. Serpentary. Cascarilla. Pepper. Contrajerva. Ginger. Capsicum. Mezereon.

_Resinous substances._--Guaiacum. Mastich, Olibanum, Myrrh, Elemi. Copaiba. Peru, Tolu. Assaf[oe]tida, Ammoniacum, Galbanum. Benzoin, Storax. Pine resin.)

This list of General Stimulants is long, but it might even be further extended. The majority are produced by the vegetable kingdom. The acrid principles to which some owe their power are intermediate in nature between volatile oils and resins. Some of them are volatile, like the former; others fixed, like the latter. Some of the resinous products contain also a volatile oil. The principles of Capsicum and Mezereon are very similar in their chemical nature to the true resins. (_Vide_ page 85.)

These remedies differ very much in power, but their influence is the same in character. They exalt nervous force in general. They seem to act on the whole nervous system; but their most obvious action is to increase the force and frequency of the pulse, and to invigorate the circulation. They are not, for the most part, very powerful medicines; and their action is seldom so violent as to be succeeded by much reaction. They improve digestion for a time, by a stimulation of the sympathetic nerves of the stomach and other viscera. In large doses they are irritants, and may impair the digestive powers, and cause headache. Though possessing no marked stimulant power over the function of mind, like that of the Inebriant Narcotics, yet they certainly exalt the activity of the brain, along with the other nervous forces.

Dr. Pereira classes the majority of Stimulants among _Ganglionics_, considering that they only act on parts supplied by the sympathetic system of nerves. But this view of their operation appears to me to be too limited; for all of them seem to have a certain action on the brain.

Thus Ammonia is used in Syncope, a state which no doubt depends upon a shock received by the brain. And there are several things which show that it relieves this state more by stimulating the brain than by merely rousing the heart and vascular system. It is found to be most effectual when inhaled through the nose; by which means it could easily pass at once into the cerebral circulation. Dr. Pereira thinks that when administered in the liquid form it can only pass into the blood as a salt, being neutralized by the stomach-acid. In this case it could only act before absorption. But it is probable that it is too diffusible and too rapidly absorbed to be entirely so neutralized; and besides, its operation when inhaled is the same as when ingested, which seems to point to an agency after absorption in the latter case. For when inhaled, it must be absorbed in the free state. And to suppose that it acts by stimulating the nerves of the stomach only, is to receive a thing for which we find no parallel in the action of medicines. (_Vide Prop. I._)

Ammonia has been used with advantage in the prevention of Epileptic fits, being given just before their expected occurrence. It could hardly be of use in this disorder unless it affected the brain.

Other General Stimulants manifest this action on the brain to a greater or less degree.

Phosphorus is a Stimulant. In small doses it quickens the pulse. It somewhat heightens the mental activity. It is said also to have an aphrodisiac operation, due to its powers as a cerebral excitor. Volatile oils possess a certain influence over the functions of the brain, as well as those of the organic nerves. Cajeput oil has been used in Hysteria; employed to control various spasmodic movements; and administered in Typhoid fevers and Asiatic Cholera, to communicate nervous power. The fetid gum resins are well known as Antispasmodics. The spasms which these medicines relieve are due to a fault in the nervous polarity, commencing generally in the brain or nerve-centres,--and are more or less subdued by general stimulators of the nervous functions. Copaiba, an oleo-resin, may cause a general febrile condition, accompanied with headache,--when given in large doses.

So obvious is the cerebral power of some volatile oils, that Turpentine, in large doses, has been known to produce inebriation. It is not generally used for its Neurotic powers, but as a Purgative or a Diuretic; or else it might have been classed among Inebriant Narcotics. I have enumerated it above among volatile oils. It may be regarded as transitional between true Stimulants and Narcotics.

Ergot of Rye is another medicine which has a double action. It is used as a Special Stimulant to the Uterus; but it is also a Narcotic to the brain.

Most General Stimulants are without any marked influence on the mind; but stimulate the organic and merely animal function of the brain, and of the Sympathetic nerve throughout the system.

Concluding that General Stimulants have all more or less the power of exalting nervous force in general, we have still to consider some other questions relating to their action.

It is maintained by some that Stimulants have simply the power of calling forth the nervous force which already exists in the system, and that they cannot create any more in addition to this. But if this were the case, then the reaction, or subsequent failure of nervous power, ought to be exactly equivalent to the first temporary increase of that power; assuming this increase to have been simply abstracted from the natural resources. But we do not find it to be so. The reaction from the effect of a Stimulant is always very slight, and often quite imperceptible.

And there seems to be no _à priori_ reason why we should not actually cause nervous force to be generated. We know that a galvanic current, or even a mechanical cause, may induce it to be suddenly and powerfully manifested. I believe that a Stimulant is able actually to produce nervous action; perhaps by an irritative operation upon nerve-fibre. So by continually repeating the dose of a Stimulant, as Ammonia or Brandy, it is possible to maintain the circulation and nervous energy at a certain level, without the occurrence of any reaction for a considerable period.

But we must take care not to confound _nervous force_ with _vital force_. The former may be very much increased, as in high inflammatory fever, without a corresponding increase of the latter. The advantage of a stimulant is regulated by this rule. When there is a failure in vital energy, no Stimulant will serve to prolong life, for it cannot communicate fresh vital power. But there may be no such failure of vital energy, and yet a sudden or accidental deficiency of nervous force may serve to peril the continuance of health, or even the tenure of life. For a certain degree of this nervous force is necessary both for life and health. When it is diminished, all the functions must suffer; when it fails entirely, the circulation must stop, and death ensues. It is in these cases that a Stimulant medicine is appropriate. It does not do good by communicating vital energy, but by remedying the want of nervous action, by which want the manifestation of the vital energy is subdued. This must always be borne in mind when the applicability of Stimulants is under consideration.

Some writers have complicated the subject by classing as Stimulants all medicines which tend, directly or indirectly, to communicate vital strength; as Tonics, and remedies which counteract morbid depressing causes. This is in direct contradiction to the rule given above. True Stimulants are only of use by counteracting that failure of nervous force which hinders the manifestation of the vital strength which is stored up somewhere in the system. For I have just observed, that to exalt nervous force is not necessarily to exalt vital force, but that any thing which tends to destroy the former must at length repress and extinguish the latter.

The above considerations apply to the action of these Stimulants on the powers of the system generally. But they may act locally. Thus in moderate doses they promote digestion, by acting on the nerves of the stomach and intestinal canal. They increase most of the secretions in passing through the glands in the blood. In both cases they exalt nervous force; but in the latter case their action is of a particular nature, and will be treated of when they are considered under the title of Eliminative medicines.

To impress the system generally, Stimulants are used when there is a failure of nervous force on account of some sudden and acute disorder, without any material undermining of the vital energies. In long chronic cases, where there is real and manifest vital debility, Tonics or blood-medicines are required. But in such a case as Syncope, or stoppage of the heart on account of a sudden nervous shock, Stimulants are particularly appropriate; also in the latter stage of Typhoid fever, or of asthenic Pneumonia, or of Cholera, where the existence of life is endangered by a great loss of nervous power. In spasmodic diseases, as Hysteria, where the health is deteriorated on account of a derangement of the nervous functions, Stimulants may be of use.

Such then appears to be the _modus operandi_, and such are the chief applications, of the remedies belonging to the order of General Stimulants. Those of the next order exert an action of the same kind, but their field of operation is on a more confined scale.

ORD. II. SPECIAL STIMULANTS.

(Strychnia; Brucia; Toxicodendron; Ergot of Rye; Borax; Rue.)

These are medicines which pass from the blood to the nerves or nerve-centres, and act so as to exalt the energy of particular nerves or sets of nerves. They do not affect the whole nervous system, but they operate on one set of nerves in the same way that General Stimulants operate on all, though usually with greater energy.

The causes of such a localized action are hid in obscurity; but it has already been hinted that they may perhaps be partly accounted for by the differences in chemical or mechanical structure existing between different parts of the nervous system.

Strychnia, the alkaloid and chief active principle of Nux Vomica, acts as a Special Stimulant, chiefly to the spinal cord and the nerves that proceed from it. Its operation is mainly exerted upon the motor branches. Thus in large doses it causes a spasmodic and powerful contraction of the muscles of the trunk, and may even produce death by rendering respiration impossible. Its action is propagated from a motor nerve to a muscle, and is kept up for some time. In small doses it is useful in certain cases of paralysis. Two things are necessary in order that it may act efficiently. The muscles of the part must be whole and sound; for if destroyed by excessive atrophy or fatty degeneration, they cannot be roused by any stimulus. The nerve, too, and the centre from which it originates, must be sound, or else the medicinal impulse cannot be conducted along it. These two conditions can only concur in paralysis from disuse, _i.e._ when the incapacity to move a limb depends merely upon its having long been in a state of inactivity, but when the lesion of the centre which caused the paralysis has at length sufficiently healed, and the nerve is now in a fit state to conduct a motor impulse.

Strychnia has no operation on the intellectual functions; neither does it act upon the sympathetic nerves of the heart and arteries, so as to quicken the pulse like ordinary stimulants. It exalts sensibility as well as irritability, but not so powerfully. It is a special Stimulant to the motor and sensory nerves throughout the body. Acting upon the spinal cord, it tends thus to exalt reflex action, which is derived from that centre. In small doses it appears to promote digestion, and may perhaps act upon the ganglionic nerves supplied to the stomach.

Brucia, which is the other alkaloid of Nux Vomica,--and the leaves of the Rhus Toxicodendron,--resemble Strychnia in their action, but are less powerful.

Ergot of Rye is a stimulant to the muscular nerves of the Uterus of the female, but to no other nerves in any marked degree. Borax and Rue possess a similar action, but are not so efficient.

When labour is retarded on account of an atony or debility of the Uterine muscle, and when also there is no obstruction or danger which can result from bringing on contraction, Ergot supplies us with a ready and effectual means of doing this. It is also efficacious in cases of uterine hæmorrhage, because the open mouths of the bleeding veins in the wall of the uterus are closed by the contraction which it causes.

When given in an over-dose, Ergot has a dangerous action on the brain, producing at some times narcotism, at other times syncope. But this is not the effect for which it is employed, and is altogether distinct from its operation as a Special Stimulant, which is exerted only upon the ganglionic nerves of the muscular uterus. In small doses it produces no other effect than this.

Like the other medicines of this order, Ergot is not an excitor of the heart and circulation. Its stimulant action is strictly local in its nature.

NARCOTICS.

This, the second division of Neurotic medicines, is in one sense intermediate between the other two divisions, but in another sense different from both of them. Narcotics are defined to be medicines which pass from the blood to the nerves or nerve-centres; which act so as first to exalt nervous force, and then to depress it; and have also a special action on the intellectual part of the brain.

This primary exaltation of nervous force is produced by some to a very considerable extent, but by others very slightly. Of the three orders into which I have divided Narcotics, which are named from their respective actions upon the brain, Inebriants cause most, and Deliriants least, of this primary stimulation. In the second place, Narcotics depress nervous influence. This depression is not in a direct, but in an inverse ratio to the primary stimulation. The less the one, the greater the other. Thus the depression cannot be considered as the mere re-action from the stimulation, as supposed by Dr. Brown, for then there would be a direct relation between the two effects. But we find that the exhilarating action of Alcohol may often be followed by no manifest depression; and that Belladonna, which scarcely stimulates at all, exerts a very sensible depressing influence.

Regarded simply in their action on nervous force generally, the medicines of the first order of Narcotics would approach very nearly to Stimulants, and those of the third order to Sedatives. But Narcotics have all a power which is possessed by neither of the other divisions.

They influence the intellectual functions, _i.e._ the mind, and the physical ties by which mind is connected with matter. These physical ties are,--the functions of volition and sensation, by which the mind is connected with the body, moving it or feeling it; and the five senses, by which the mind, through the body, is connected with external things. These intellectual properties, the centre of which is the brain, are more or less affected by Narcotic medicines. The first action of the latter is, to exalt these functions, just as they first exalt nervous force in general. The degree of this exaltation varies, as in the former case. Inebriants stimulate the mind to a considerable degree; Soporifics less; and Deliriants possess least of this primary exciting power. But it is in their secondary action on the mind that we find the most characteristic difference between them.

On referring to the arrangement, it will be seen that I have divided Narcotics into the three orders to which I have already referred by name, and which are thus designated in Latin:

NARCOTICA.

Ord. 1. Inebriantia. Ord. 2. Somnifera. Ord. 3. Deliriantia.

These Orders are named from the secondary action of these different Narcotics on the intellectual functions. In the production of inebriation these functions are impaired and deranged; in sleep they are lulled or extinguished for a time; and in delirium they are excited and led astray. The several actions of these orders will be more minutely described presently, and the individual medicines of which they are composed will be shown to agree with the general definition of Narcotics.

Dr. A. Billing considers that Stimulants call forth nervous force, and Sedatives depress it; and that Narcotics do neither the one nor the other, but merely impede its communication. I do not consider this distinction to be quite correct. Narcotics exert in the first place a stimulant, and in the second place a sedative action; but these actions have no relation in degree, for one of them always exceeds the other, as we have just seen. Thus in the whole effect, either the stimulation must exceed the depression, or the depression must be greater than the stimulation. So that in one way or the other the quality of nervous influence must be altered.

The medicines of the first order of Narcotics resemble Stimulants so far as this, that they tend altogether to increase the amount of nervous force. Perhaps Tobacco and Lobelia are exceptions to this. The medicines of the third order, and some of those in the second, tend on the whole to diminish the quantity of nervous force, and are thus akin to Sedatives. A correct understanding of the differences in action which exist between the groups of Neurotic medicines is, I think, very essential to a right application of these remedies in the treatment of disease.

ORD. I. INEBRIANTIA.

(Alcohol; Wine; Ethers; Chloroform; Camphor; Indian Hemp; Tobacco; Lobelia.)

The medicines of this order, taking Alcohol as the type, approach more nearly to Stimulants than any other Narcotics. When given in small doses, their narcotic operation may hardly be perceived. They are then exhilarants; slightly quickening the pulse, and enlivening the mental faculties. When given in large doses, this stimulating action on the heart and mental powers occurs first, and is now more intense; but it is soon succeeded by disturbance and impairment of the intellectual functions. The secondary depression of the heart is comparatively feeble, except in the case of Tobacco and Lobelia, which are exceptional members of this order.

The disturbance of the mind produced by these medicines is not of a partial, but of a general character, extending to all the intellectual functions. It is called Inebriation, or drunkenness, and may exist in various degrees. The mind itself is confused and bewildered; volition is impaired, so that the man staggers in his walk; and the powers of the senses are disordered or lost. This condition, when carried to an excess, results in stupefaction, coma, and death. These are the several degrees of the same action, which is a general impairment of all the intellectual functions.

Alcohol and the Ethers produce the primary exhilaration in the greatest degree; Tobacco and Lobelia, in the least. Though varying in degree, yet, as far as the stage of inebriation, the effects of these medicines are similar in kind.

Stupefaction constitutes the next stage of the action of Alcohol, Camphor, Indian Hemp, Ether, and Chloroform. Camphor and Indian Hemp exert at this period an anodyne influence; to which also, in the case of Indian Hemp, may be added a very curious imitation of Catalepsy. Ether and Chloroform have at this time a peculiar action in extinguishing the sense of Feeling. With this object they are commonly administered by inhalation in painful surgical operations.

The stupefaction produced by the above medicines is not at all prominent in the case of Tobacco and Lobelia inflata. Instead of that they both exert a particular sedative action on the heart and circulation. This is accompanied with nausea, and with great relaxation of the muscular system, like that which is produced by Antimony. It may lead to syncope and death.

Syncope has been known to be suddenly produced in some cases of the inhalation of Ether and Chloroform. These two medicines are also muscular relaxers, like Tobacco.

The cases which demand the employment of these medicines, as also of the other Narcotics and Sedatives, will be considered at the close of the section treating of Neurotics, and again when some of them are separately described in the fourth chapter.

ORD. II. SOPORIFICS.

(Opium. Lactuca. Hops. Nutmegs.)

Opium, which is the chief and only important medicine of this order, may be considered as the type of Narcotics. It causes in the first place a slight quickening of the pulse, and some excitement of the mental faculties. It is named from its peculiar secondary action on the latter. It produces drowsiness and sleep.

We have seen that the term _intellectual function_ must be understood to include not only the mind itself, but also the powers of volition and sensation, by which the mind is connected with the body,--and the five senses, by which it is enabled to appreciate the external world.

Inebriants affect these three in about the same ratio. Ordinarily they impair the mind, and derange the functions with which it is connected; but they do not quite extinguish either volition, sensation, or the special senses. Soporifics differ from this action in two ways. In sleep the mind may remain active; but it is left alone, dreaming, and uncontrolled by physical ties. For the functions of volition and sensation, and the special senses of Sight, Hearing, Smell, and Taste, are entirely suspended in perfect sleep. So that while Inebriants affect similarly both the mind and the natural functions with which it is connected, Soporifics may leave the first untouched, but they entirely subdue the latter. The condition of sleep differs also in another important particular from the state of inebriation,--as well as from delirium, which we shall have presently to consider. Sleep is liable to be suddenly interrupted or suspended by comparatively slight causes, as a physical shock, or a forcible impression upon one of the senses which are held in abeyance and subjection. Neither inebriation nor delirium can be suddenly put an end to in this way.

Such appears to be the distinction between the operations of these two orders of medicines.

Pain prevents sleep, because it enforces sensation. Thus a mere Soporific, if effectual, would prove anodyne, and relieve pain.

But Opium has an important anodyne action, which is independent of its power of producing sleep, for it may occur without the latter. It is by far the best remedy for pain in the whole catalogue of medicines. It also produces relaxation of the muscular system, and is thus a powerful antispasmodic. In excessive dose it produces a marked sedative effect; causing an imperceptible or irregular pulse, and very slow breathing, with contraction of the pupil of the eye. It may kill by apn[oe]a; _i.e._ by stopping the respiration.

Tobacco resembles Opium in causing contraction of the pupil, and relaxation of muscular fibre. But it is inebriant, and not soporific; and its secondary sedative action on the heart is more powerful than that of Opium. The order of Deliriants dilate the pupil. Inebriants and Deliriants act on the glands as Eliminatives, being mostly diuretic. Opium has a contrary action; it diminishes all the secretions except that of the skin, which it increases in amount. Most particularly it diminishes the secretion of the bowels, causing constipation. At the same time it impairs the appetite and digestive power, producing often nausea, and coating the tongue. It tends also to produce a determination of blood to the head.

Lettuce, from which Lactucarium is prepared, resembles Opium in its action, but is neither so powerful nor so efficient. Nutmeg and Hops have proved Soporifics when given in large doses.

The relief of pain, and the production of sleep, are about the commonest and the most grateful of the offices which fall to the lot of the physician; and in either case Opium, or one of its preparations, may be said to be indispensable. But a certain caution and care must be exercised, even in the administration of this most useful remedy. (_Vide Art. Opium_, Chap. IV.)

ORD. III. DELIRIANTS.

(Hyoscyamus; Belladonna; Stramonium.)

These medicines are all produced by the natural order Solanaceæ. Of all Narcotics they approach the nearest to Sedatives. Their only stimulating action is to produce at the very first a slight and evanescent febrile condition,--a quick pulse and heat of skin,--which never lasts long, and is sometimes overlooked.

They are not Soporific. Their action is soon manifested by an anodyne operation, and a sedative influence on the heart and circulation. For this double action they are employed in medicine, being used in painful disorders, fevers, and inflammations. As anodynes they are not so efficacious as Opium, but their action is not followed by constipation, or by a diminution in any of the secretions.

They all dilate the pupil of the eye. Belladonna produces a peculiar dryness of the throat, and has been known to cause an erythematous eruption. Stramonium appears especially to control the respiratory nerves, and is thus used in Asthma, where there is a spasmodic circular contraction of the smaller bronchial tubes. Lobelia, a medicine of the first order, possesses a somewhat similar power. The action of the remedies of this third order of Narcotics is distinguished by the production of delirium when they are given in large doses.

Let us again assume the threefold division of the mental functions, to which allusion has already been made. Inebriants impair equally the mind, volition, and the five senses. Soporifics extinguish for awhile both volition and the senses, but may leave the mind alone. In delirium these functions are not thus impaired and held in subjection, but they are excited and led astray. The mind is occupied intently upon imaginary fancies; unreal objects and hallucinations are presented to the senses. So that Deliriants, in this peculiar phase of their action, tend to excite the mind and the volition, and to delude or derange the senses.

Speaking generally and rather inaccurately, we might say that the medicines of the first order of Narcotics bewilder and impair the powers of the mind; those of the second order subdue and extinguish them for awhile; and those of the third kind excite and derange them.

Certain peculiar and exceptional effects are produced by some Narcotics when they are administered in repeated doses for a long time together. Taken in this way, Alcohol produces delirium tremens, and great despondency of mind; as also often a chronic inflammation of the liver. The continued smoking of Tobacco is found to exert a tranquilizing influence over the mind. And the continual use of Opium or Indian Hemp, both of which are habitually consumed in large quantities in the East, produces a curious and melancholy series of mental hallucinations and disorders.

SEDATIVES.

We have now to consider the third and last division of Neurotic medicines. Sedatives are medicines which directly depress nervous force. Some affect nervous force in general; others confine their action to particular nerves. They are mostly energetic and dangerous agents. For the time being they may destroy nervous power, and remove nervous control.

It might already have been concluded, from what has been said of the secondary action of Narcotics, that there are two ways in which a Sedative action on nerve may be manifested. Sedatives may destroy nervous influence; or they may simply derange it.

Let us suppose a special Sedative to derange the action of the Vagus nerve. It would probably cause the rhythmical contraction of the heart to be abnormally slow or irregular. It would be likely to diminish in the lungs the sensation of want of breath, and thus decrease the number of the respirations; and at the same time it would repress the irritability of the pulmonary mucous surface. Further, it would in some way derange the normal function of the stomach. All these things a Sedative to the Vagus nerve does actually effect. Given in large quantity, it may cause death, by destroying those functions which in a small dose it deranges.

All the varieties in action of Sedative medicines may be accounted for by considering that they may either derange or destroy the nervous forces. In the case of each set of nerves in the body we may distinguish an action of derangement, and an action of destruction, both producible by Sedative medicines. Thus by an action on the motor nerves of the cerebro-spinal system, convulsions or paralysis may be produced. By an influence on the nerves of sensation; pain, or anæsthesia. By an affection of the organic nerves of the heart, or of the brain which controls them; palpitation, or syncope. By an action on the nerves of the lungs; cough, or apn[oe]a. By the exertion of a sedative power over those of the stomach, nausea may result, or vomiting. These various symptoms are all brought about by Sedative medicines, but in each case the first effect is referrible to a derangement, the second to a loss of nervous power. In every instance there is an impairment of natural nervous force.

Narcotics act on the mind. They cause death, with stupor or delirium. Sedatives act on the organic function of the brain, which is necessary to life, but they do not affect the mind. In poisonous doses, they kill by producing syncope, which is a suspension of the action of the heart. Hydrocyanic acid causes at the same time convulsions. These convulsions appear to be caused by a derangement of the nervous polarity of the spinal cord; and not by a stimulation of this centre, as the tonic spasm of Strychnia. (_Vide_ page 232.)

Sedatives are divided into two orders, according to the extent of their action; in the same way as Stimulants have been divided.

SEDANTIA.

Ord. 1. Sedantia Generalia. Ord. 2. Sedantia Specifica.

General Sedatives have a direct action upon all the nerves and nerve-centres in the body, the result of which is a diminution of nervous force.

Special Sedatives exert the same depressing action upon particular nerves only. Like the order of Special Stimulants, they are peculiar and exceptional agents. All those with which we are acquainted appear to direct their action to the branches of the Vagus nerve.

It is among General Sedatives that the types or representatives of this division are to be found. The definition of this order does not admit of so great a variety in action as must be allowed to Narcotics. A Stimulant medicine simply exalts or increases nervous force; and a Sedative simply depresses the same. But a Narcotic first does one thing and then the other; and according to the degrees of these two actions, so do some Narcotics resemble Stimulants, and others approach very nearly to Sedatives. But we have seen that Narcotics have also a peculiar and mysterious action on the mind, which action is of three separate kinds. And the same three orders which are named according to their respective actions on the mind, are found to coincide with three stages of transition from the action of a Stimulant to that of a Sedative medicine.

It is impossible to associate in the same prescription a Stimulant and a Sedative medicine; for their actions are directly contrary, and tend to counteract one another. But it is often desirable to prescribe an Inebriant Narcotic with a Stimulant, for their actions resemble each other so much, that they are able to work together. And Deliriants, which stand at the other end of the Narcotic scale, may often advantageously be given with Sedatives, which they very much resemble in their nervous operation. Thus, on the one head, Brandy may be given with Ammonia; on the other hand, Hyoscyamus may be prescribed with Digitalis or Hydrocyanic acid.

ORD. I. GENERAL SEDATIVES.

(Hydrocyanic acid. Creosote. Aconite. Conium. Colchicum. Tea and Coffee.)

These are medicines which pass into the stomach, and are capable of absorption; which are absorbed, and are proved to act after passage into the blood. From the blood they pass to the nerves and nerve-centres, and on all of them alike exert a depressing influence. Some of them are much more powerful than others. They do not exert any primary stimulant effect, or any action on the intellectual part of the brain. Most of them have special actions and tendencies.

Hydrocyanic acid is a powerful and dangerous medicine. In large doses it very rapidly takes effect, producing convulsions, syncope, and death. In small doses it is anodyne, and antispasmodic. It is considered especially to influence the reflex spinal system, and by this means may allay convulsive cough, and quiet spasmodic movement. It is very useful in Gastrodynia, and appears then to act locally upon the painful and irritable nerves of the stomach.

Creosote stands, as a medicine, between Hydrocyanic acid and Turpentine. It has a double action; being anodyne, like the former; and a mucous stimulant, like the latter. Moreover, it is a true Astringent, which cannot be said of Turpentine. It is not powerful as a Sedative, but its peculiarity of action often renders it useful in Gastrodynia. It is particularly applicable when pain in the stomach is accompanied with a tendency to hæmorrhage, or with a probable relaxation of the mucous coat.

Aconite is a powerful anæsthetic to the superficial sensory nerves. When applied in solution or ointment to the surface of the skin, it produces first some heat and tingling, which is attributable to a derangement of the nervous influence; and this is succeeded by perfect numbness. It is thus a most valuable topical remedy in true irritative Neuralgia. Other Sedatives and Narcotics have the same power as topical anodynes, but not in so marked a degree. In large doses Aconite is a General Sedative; producing tingling of the extremities, vomiting, and syncope; and affecting the brain in various ways, as will be shown by some experiments which I have made upon its action, to be detailed in the fourth chapter. An alkaloid called Aconitina, the most powerful of all known medicines, is the active principle of this drug.

Conium (Hemlock) also owes its properties to the alkaloid Conia. Dr. Christison has made some experiments upon the latter. He found that it produced swiftly-spreading paralysis of the motor nerves; and he considers it to act particularly as a Sedative to the reflex spinal functions. It also paralyzes the sensory nerves, but in a less degree.

Conium is certainly anodyne; and produces often a sedative action on the heart. It would thus appear to be a General Sedative. But in some recorded cases of poisoning by Hemlock, coma has been mentioned as a leading symptom. Were this to be authenticated, and shown to be the invariable result of the action of this medicine in large doses, then it ought certainly to be classed among Narcotics. Dr. Pereira considers it likely that the plant contains more than one active principle. Hemlock has a paralyzing action on the nerves of motion, which is directly the reverse of the stimulating action of Strychnia; and is thus of use in cases of convulsion and spasm. It is also often prescribed as an anodyne.

Conium is further said to have a curious resolvent power over glandular enlargements, and to have thus frequently caused their absorption and disappearance. This action was first noticed and described by Dr. Fothergill. All true resolvents operate by an action in the blood, but it is difficult to conceive how such an action can be exerted by a nerve-medicine. It may possibly act indirectly by quieting the action of the heart, and controlling an irritable state of the nervous system. In the same way Opium often appears to act as a resolvent. And it is certain that Hemlock, when used for this purpose, very often fails altogether. It has been wrongfully extolled as a panacea in Phthisis; but is in fact of no greater use in that disorder than Hyoscyamus, Prussic acid, and other medicines which reduce the pulse. For the patient in this disease is devoured by a continual slow fever, and any thing which tends to lower this fever will serve to prolong his existence. But altogether it must be admitted that considerable mystery attaches to the operation of this medicine.

Colchicum has many different actions. It has an agency in the blood, being Antiarthritic. It is an Eliminative, acting on the liver and bowels. And it is also a General Sedative. To the combination of an eliminative with a sedative or anodyne action, the use of Colchicum in Gout has been, I think, erroneously ascribed. For in fact it seems to act best in this disorder when it causes no purging, and scarcely any action on the nerves. When it has been long used, it causes a great depression of the spirits, like that which may be caused by some undoubted blood-medicines, as Mercury. But it does not affect the understanding, or the special senses. In poisonous doses it depresses the circulation and the nerves generally, but it causes no stupor or insensibility. It is therefore not a Narcotic; but, like other Sedatives, it kills by syncope.

In the behaviour of the system towards Colchicum, Aconite, Digitalis, and other nerve-medicines, there are two peculiarities which are worthy of remark. They are called _cumulation_ and _toleration_.

Some quantity of the medicine may often be given, in repeated doses for some time together, without any apparent result. It seems to remain in the blood, and to become accumulated or stored up there. But all on a sudden it breaks out, appearing to be discharged on the nerves, and may produce very dangerous symptoms. This _cumulative_ action is especially observed of Digitalis, and therefore considerable care is required in the exhibition of that medicine. This medicine is a Special Sedative, and will be presently considered as such. In other cases we find that the nervous system becomes by degrees inured to the effect of a particular medicine, and suffers less by its presence than it did at first. This is called _toleration_. It is particularly observed of Colchicum and of Antimony, and of all medicines which act on the Vagus nerve so as to cause vomiting.

Tea and Coffee, common articles of diet, are slightly sedative to the nervous system generally. They lower the pulse, and, by diminishing congestion of the brain, tend to clear and tranquilize the action of the mind. This activity of thought is endangered by the cerebral congestion which exists early in the morning, on account of recent sleep,--and again towards the evening, from the full meal of the middle of the day. It is thus at these times that they are found so useful, and are so universally adopted. They are, in fact, almost indispensable to the daily existence of civilized man, with whom a continual energy of mind is a necessary of life. Infusions of these substances, or of materials similar to them in medicinal nature, are adopted as a daily beverage by all civilized nations. By diminishing congestion of the brain, Tea and Coffee have not only the effect of clearing the mind, but in large quantities they induce wakefulness. This is particularly the case with Coffee. It is not clear that Tea, as commonly drunk, is ever unwholesome. Green Tea is a more powerful sedative, and resembles Coffee. Coffee has a more potent influence over the mind and nervous system than is possessed by Tea, and is apt to disagree with many persons. Like Opium, but in a far less degree, Coffee tends to confine the bowels. By diminishing the congestion of the brain which is produced by Opium, strong Coffee is of use in cases of poisoning by the latter substance.

Tea and Coffee are sometimes said to be mental exhilarants; but they only become so indirectly, by removing congestion, which is a cause of stupidity.

Both Tea and Coffee contain the alkaloid Theine; but it is probable that their Neurotic action is not so much owing to this, as to a volatile oil, which exists in both in some quantity.

ORD. II. SPECIAL SEDATIVES.

(Antimonials. Ipecacuanha. Digitalis.)

These are medicines which, like the last, depress nervous force, yet they do not exert their influence on the nervous system as a whole, but only on certain parts of it. So far they resemble Special Stimulants; but their effect is of a directly opposite nature. They have also no direct influence on any part of the brain.

Antimony, Ipecacuanha, and Digitalis, have each of them a number of different actions. The first has already been included among Catalytic Hæmatics, as tending to counteract in the blood the process of inflammation. But it possesses further a Neurotic power, by which it is gifted indirectly with a more powerful control over acute inflammations than could be exerted by any slow-acting blood-medicine. It is also Eliminative. Passing out of the body through the glands of the skin, it becomes a Diaphoretic. This may be its only action when it is given in doses too small to act upon the nerves. It must not be confounded with the diaphoresis which accompanies the condition of nausea, and which is probably produced in another way. Ipecacuanha is in the first place a Neurotic, of less power than Antimony; in the second place an Eliminative, increasing expectoration, as well as Diaphoresis. Digitalis too acts first upon the nervous system; then on the kidneys, being a Diuretic.

But we are now concerned with the special Neurotic actions of this group of medicines. They all exert an influence over the three functions of respiration, circulation, and digestion. They affect the heart, lungs, and stomach, parts which are supplied by the branches of the Vagus nerve, as well as by the Sympathetic. Their action is not an external action, for it is produced when they are introduced into the blood at any part. Thus Tartar Emetic or Ipecacuanha, when injected in solution into one of the veins, will cause vomiting. M. Magendie has found that in the case of dogs they also produce Pneumonia. The mere inhalation of the dust of Ipecacuanha has been found to act upon the lungs so as to cause Bronchitis. These actions, as well as the various effects which are found to follow the introduction of these medicines into the stomach, can only be explained satisfactorily by supposing that they act as Sedatives to the branches of the Vagus nerve, thereby deranging or destroying the natural influence of that nerve in the direction and regulation of the organs which it supplies. For we have already seen that the action of a Sedative medicine is of such a nature as to derange nervous force in some cases, and simply subdue it in others.

These actions are obviously nervous actions; for they are quick, sudden, and transient, and confined to parts supplied by a particular nerve. They are exerted upon nervous forces, and not upon the blood. If then they are nervous operations, they must either be directed towards the Vagus, or to the Sympathetic nerve, for these are the only nerves which supply the parts influenced by these medicines. They cannot act upon the Sympathetic, for two reasons. If they did so, we might reasonably expect that the other parts of this nerve would be influenced at the same time. But this does not appear to be the case. And again, an action upon the Sympathetic nerve could not be suddenly and violently evidenced, for the natural action of this nerve is slow, chronic, and persistent. At all events, the effects for which they are used could not be produced by an affection of this nerve.

We may therefore conclude that the action of these medicines is exerted upon the Vagus nerve and its branches. They affect the different parts of the Vagus nerve in variable proportion.

Some apparent anomalies in their physiological influence may be explained by considering the peculiarities which attach to all sedative actions. Thus we have seen that when given in large doses to healthy persons, Hydrocyanic acid produces convulsions by deranging the reflex spinal functions; and that in convulsive affections, when the same functions are disordered, the same remedy may do good by subduing their excited condition. On similar grounds, Tartar Emetic, injected into the veins, may produce Pneumonia; and Ipecacuanha, introduced as dust into the lungs, causes Bronchitis or Asthma; and yet Tartar Emetic is advantageously employed in the cure of Pneumonia, and Ipecacuanha is a remedy for Bronchitis. When the function of the healthy nerve, or that part supplied to the lungs, is deranged to a certain degree, an inflammation of the mucous membrane or substance of the lung is a natural result. But when these tissues are already inflamed, a course of medicine, which at the same time subdues the action of the heart, and represses the irritability of the nerve supplied to the part will be likely to effect a cure. They are both sedative actions; but the first is an action of derangement, the second one of depression. This seems to me to be the correct explanation of a difficult matter.

It was just now observed that these medicines affect the functions of the Vagus in different proportions.

The action of Ipecacuanha, when given in repeated small doses, is particularly directed to the pulmonary organs. It allays the sensation of want of breath, and diminishes the cough, of Bronchitis. In larger doses it produces first nausea, then vomiting.

Still more decided nausea is produced by Tartar Emetic. It is followed by vomiting when the dose is sufficiently large. Nausea consists in a sensation of discomfort about the præcordial region, which is due to a derangement of the stomach, with a feeling of great languor, a cold perspiration and tremor, and at the same time a striking depression of the action of the heart. This nausea may be caused without vomiting, by a regulation of the dose. On account of the depression of the heart's action, which is its chief symptom, it is often very desirable to cause nausea in acute inflammations and fevers. It is kept up by the careful administration of Tartar Emetic. It may not be so desirable to produce vomiting; for this is accompanied with great vascular excitement and active congestion of the brain. And yet it is found that the more Antimony we can get into the blood, the more potent and durable will its antiphlogistic influence be. For this medicine appears to possess a blood-action as well as an action on nerve. Experience has shown that if the dose of Tartar Emetic be gradually increased on each repetition, it may often be tolerated by the system; that is, it does not produce vomiting; and then the remedy, being absorbed, is better able to continue its antiphlogistic and nauseating action. For the act of vomiting, besides other bad consequences, causes the rejection of that part of the antimonial which has not been absorbed. By the operation of the Nauseant the violent action of the heart in high fever may be allayed. It is often of signal efficacy, most especially in Pneumonia.

Digitalis given in large doses may also act on the stomach, and cause vomiting. This operation has been ascribed, erroneously, as I think, to an irritating action possessed by this drug. But in smaller doses it affects the heart and circulation powerfully, without producing the other symptoms of nausea. It depresses the action of the heart. Sometimes the rapidity of the beat is slightly increased at the first, but the pulse at the same time is weaker. It soon becomes slower and sometimes irregular. This action is characteristic of derangement of the Vagus nerve. For it was found, in some experiments on animals made by M. Weber, that when the function of this nerve was disturbed by mechanical irritation, the rate of the heart was first accelerated, its action then became slow and irregular,--and finally it stopped. There cannot be a greater mistake than an attempt to explain such a derangement by supposing this medicine to exert a primary stimulant action. Coincident with the quickening of the pulse, there is a manifest loss of power.

Digitalis is especially useful in dropsies which result from an obstruction to the cardiac circulation. By subduing the action of the heart, it relieves that congestion of the vascular system which is the cause of the effusion of serum. But it is also a Diuretic; and may thus too relieve the loaded vessels by carrying off in the urine some of the water of the blood.

Such is an outline of the action of Special Sedatives to the Vagus nerve. It is not clear whether they affect that nerve at its origin in the brain, or whether they act the extremities of its filaments.

These Sedatives do not act directly upon the brain itself. But indirectly they may affect it, when given in large doses. For by depressing the action of the heart they cut off the natural supply of blood to the brain, and may, by so doing, produce delirium and convulsions. They tend obviously to kill by syncope. Some medicines may cause syncope by an action upon the brain. General Sedatives may do so; but it does not appear that the medicines of this order ever act in this way.

Some other medicines rest very closely upon the confines of this order. Squill is the chief of these. It is not quite clear whether Squill should be regarded as a Special Sedative, or considered simply as an irritant Emetic and Eliminative. It is a valuable Expectorant. It is also a Diuretic; and from the analogy of its operation to that of Digitalis (_vide supra_,) and because it appears to be a specific Emetic, it is most probably a true Neurotic.

But we must not confound with Neurotics those medicines which exert a slow operation in the blood which results at length in a nervous affection. This may take place, to a greater or less degree, with all Catalytic Hæmatics. Lead, which is anti-convulsive and astringent, approaches nearest of all to the recognised nerve-medicines. After existing for some time in the blood, it produces local palsy, particularly of the muscles about the wrist; and it sometimes affects the sensory nerves, causing sharp shooting pains in the limbs. These nervous symptoms are caused by the accumulation in the system of the poison of lead, and the deterioration of the blood which is thereby produced. In the case of the palsy, we cannot certainly say whether these causes operate first upon the motor nerves, or upon the muscles themselves.

Lead certainly has some tendency to affect the brain. All kinds of brain disorders may occur in cases of chronic lead-poisoning. The metal has been found in the brain after death; but it also exists at the same time in other parts of the body. In cases of Lead-colic there is generally a paralysis of the muscular fibre of a certain portion of the intestine. The pain of the disorder is caused by an irritation of the nerves of the part.

Neurotics are medicines which tend, immediately they enter the blood, to be discharged from it upon the nervous system. They therefore immediately affect the latter. Hæmatics, in small doses, pass through the blood without exerting any direct effect upon the nerves. They are never discharged upon the nervous system except after they have for some time existed in the blood in such quantity as materially to vitiate its healthy character. Corrosive poisons affect the nerves by a violent revulsive action; and are not to be considered in the same category as medicines. Thus Lead is not a true Neurotic, but a blood-medicine. (_Vide_ page 175.)

We have now concluded our brief review of the action of Neurotic medicines. Some few will be again treated of in the fourth chapter. The views of their operation which I have wished to substantiate are in many cases the same as those which are generally adopted, in some cases different from them. In either instance I have attempted to base them on observation, or on simple inductive reasoning.

It has already been observed that these nerve-medicines are more rapid and more evanescent in their action than those which preceded them. They are unable, as a general rule, to produce a permanent effect. When such a permanent impression is desired, an approach to it can be made by a continual repetition of the dose, by which a transitory action may be constantly renewed and kept up. In other cases a mere transitory action may produce a cure. This may be the case in a sudden and dangerous emergency, which will pass over if the system can be supported through it, but which threatens life while it lasts. Or in Neuralgia, if the irritability of the sensory nerve be continually blunted by the external application of Aconite, it may at last subside altogether, and a right condition of things be restored. The same may be said of convulsive disorders, and the stimulant antispasmodics which are used to control them.

Neurotics are mostly employed in temporary emergencies. In such cases their action is often decisive and gratifying. Vital action may be restored and kept up; or excess of action allayed. Pain may be suddenly and effectually removed; delirium or convulsions subdued. Sleep may be substituted for wakefulness, or activity for torpor. By these powerful remedies we are enabled to exert an immense control over the varied manifestations of nervous force; and may often, when we wish it, substitute one condition for another which is the reverse of it. When there is a deficiency of nervous force, we make use of a Stimulant, or of one of the Inebriant Narcotics; when there is an excess of the same, we employ a Sedative, or one of the latter two Narcotic orders.

But when we desire to quell a long-standing and firmly-rooted disorder, which is not displayed by violent outward manifestations, but is nevertheless working fatally within, we must then call to our aid some Hæmatic medicine, which alone can be of permanent efficacy in such a case.

PROP. IX.--_That a third class of medicines, called_ ASTRINGENTS, _act by passing from the blood to muscular fibre, which they excite to contraction._

Although this class of Astringents is a small and comparatively unimportant class, yet it is necessary to separate it from all the others, because the medicines which compose it are completely distinct in their mode of operation. They do not necessarily act in the blood, although many Hæmatics are also astringent. They do not pass from the blood to the nerves. They do not always act by passing out of the body through the glands. Their operation is peculiar, but it is simple. As Neurotics act directly on nerve, so these act directly and especially on muscular fibre. They cause this to contract, whether it be striped and voluntary, or of the involuntary unstriped kind.

Their action is more readily understood, because it can actually be seen. It takes place out of the body, or in the body--externally, or internally. Nearly all astringents have the power of coagulating or precipitating albumen. By virtue of this power they are enabled to constrict many dead animal matters. They affect fibrinous tissues in a similar chemical way. But they seem to possess a further dynamical influence over living tissues, which possibly depends in some way on this chemical property. This dynamical influence is, as I have said, to cause the contraction of muscular fibre. By this all their operations can be explained. Taken into the blood in a state of solution, they pass through the walls of the capillaries to the muscular tissue. By inducing the fibre of the voluntary muscles to contract, Astringents may brace the system, and simulate the action of Tonics. But as the contraction of voluntary muscle is short and brief, it requires for its maintenance a continual excitation, and unless the medicine is thus continually repeated, the tonic effect subsides. But astringents further contract involuntary muscle. This contraction is slower, and more durable and important in its results. Unstriped muscular fibres exist in the middle coat of arteries, in the walls of capillary vessels, in the lining of the ducts of glands generally, and in the substance of the heart and the coats of the stomach and intestines. Astringents are irritant and poisonous in large doses. But in small doses they constrict and stimulate to a healthy condition these tubes that contain in their coats the unstriped fibre. By diminishing the caliber of the capillary vessels generally, they promote health, and counteract a lax state of the system. By the same action on the extreme vessels, they prevent hæmorrhages. By constricting the ducts of the glands they diminish the secretion of those glands, because denying it an exit. By acting on the stomach and intestines, they are able to give them tone, to diminish their secretions when excessive, and thus to promote digestion.

Having premised this general view of their action, we may now proceed to prove the Proposition in which it is stated, dividing it first into four minor propositions.

_m. p. 1._--That they are medicines which pass into the blood.

_m. p. 2._--That they have the power of causing the contraction of muscular fibre, living or dead.

_m. p. 3._--That their operation is to diminish secretion, to repress hæmorrhage, and to give tone to the muscular system.

_m. p. 4._--That these results are to be accounted for by their action on muscular fibre, to which they pass from the blood.

These assertions are an extension of the major proposition, but their establishment is necessary to a correct understanding of the latter. Their proof is comparatively easy and simple. It is not supposed to be a certainty; but simply to amount to a strong probability, which is as much as we have a right to expect in such cases.

Astringents constitute the third class of medicines which operate on the system after being introduced into the stomach. Their action is, however, of so simple a kind, that it may be exerted on the external surface in the same way as in the interior of the body. It will be seen by a reference to the table of medicines, that the class of Astringents is there divided into two orders.

ASTRINGENTIA.

Ord. 1. Astringentia Mineralia. Ord. 2. Astringentia Vegetabilia.

The lists of these orders are given below. With regard to the first minor proposition, it has already been proved that most of these medicines pass into the blood. The minerals included in the first order have already been noticed as Hæmatic medicines. They are all soluble in water. They are absorbed in the stomach and intestines, and pass into the blood. Many of them pass on into the secretions. The astringent parts of the vegetables of the second order are also soluble. Tannic acid is the chief of them; it is simply an Astringent; it has been found in the blood, where it changes into Gallic acid, and in that form it passes into the secretion of urine.

What then are the active properties of these medicines? They have all a certain chemical power; and a certain dynamical power. All the mineral Astringents have the power of precipitating an albuminous solution. So also do Tannic acid, Turpentine, and Creosote, coagulate albumen. Tannic acid precipitates Gelatine too. The dynamical property, which is common to all of these substances, is a power of causing the contraction of muscular fibre. It seems to depend somehow on the chemical power just mentioned; for Astringents appear to constringe fibrinous as well as albuminous tissues by a chemical action. They also coagulate fluids and discharges which contain albumen.

When the solution of any Astringent is applied to a fresh fibre of dead muscle placed under the microscope, it is seen to contract. The power which they possess in causing the contraction of living blood-vessels may be witnessed in a similar way. The astringent solution may be applied to the web of a frog's foot, confined in an extended position. This web is traversed in all directions by minute ramifying capillaries; and these are found gradually to diminish in caliber. In the same way as the mechanical irritation of a small artery will act upon the unstriped muscular fibre contained in its coat, and thus cause the vessel to contract at one point; so it seems that an Astringent, by a chemical action on the same muscular tissue, is able to cause the capillary vessels seen under the microscope to contract and diminish in size. At all events we may conclude, both from actual experiment and from a comparison of their several operations, that Astringents are able to cause the contraction of muscular fibre.

In the third minor proposition the chief results of their operation are stated. These have already been briefly described.

They check secretion. They are thus prescribed when any secretion is excessive. The Tannic vegetables are given in diarrh[oe]a; Nitrate of Bismuth is administered in Pyrosis; Sulphuric acid in profuse perspirations; Uvæ Ursi in mucous flux from the bladder.

They repress hæmorrhage. Thus Acetate of lead is employed in hæmoptysis; Creosote and Uvæ Ursi are used in hæmorrhage from the stomach or bladder; and the vegetable Astringents are prescribed in Dysentery.

They give tone to the system. They do this when there exists an over-relaxation of the solid fibres on account of any depressing cause, by exciting the muscles to a more or less permanent contraction, and by constringing the capillary vessels generally.

In the fourth place, it is maintained that their action in all these instances may be explained by a reference to their power in causing the contraction of muscular fibre; inasmuch as they are found to diminish the caliber of certain tubes and cavities, and these owe the contractility which they possess to the muscular fibre which is contained in their coats. It follows then from the rule of local access, that before they can influence these tissues they must pass directly to them from the blood.

Such appears to be the simplest and the most rational explanation of the action of Astringent medicines.

ORD. I. MINERAL ASTRINGENTS.

(Sulphuric, Nitric, and Hydrochloric acids. Acetate and Diacetate of Lead; Sulphate and Sesquichloride of Iron; Alum; Sulphate of Zinc; Sulphate of Copper; Bichloride of Mercury; Nitrate of Silver.)

These medicines have already been noticed among Restorative and Catalytic Hæmatics. Their Astringent action on muscle is of much less moment than their important operations in the blood. Neither is it theoretically a matter of so much difficulty; for it appears, as we have seen, to admit of a simple explanation.

By their chemical action on albumen, these substances coagulate blood, and thus act in a simple way as styptics when applied to bleeding parts externally. They form peculiar insoluble compounds both with albumen and fibrine, and it is probably by virtue of their action on the latter that they are able to cause the contraction of muscular fibre, which is a fibrinous tissue. The constriction, set up chemically, is apparently continued and propagated by the vital force of the muscle.

The most important only of the mineral Astringents are mentioned above. It must not be supposed, when their chemical actions are mentioned, that such actions are always allowed free play in the living and circulating blood. They are no doubt constrained by various forces from operating there, or else the consequences of such a disturbance of the condition of the elements of the blood would be dangerous in the extreme. (_Vide_ page 104.) They act, before entry into the blood, on mucous membranes and external parts; and on coming out of the blood, on the terminal capillary vessels, on the ducts of glands, and on mucous membranes again.

Astringents act very much alike on external parts; only that some are more soluble than others, and some excel the rest in chemical activity. But they differ considerably in their applicability for internal use. They must be given in such quantity that, after absorption and dilution by the whole mass of the blood, they may still be capable of exerting a perceptible action on distant parts. A small portion of one of them will not suffice to repress hæmorrhage, or to diminish a super-abundant secretion.

From this it follows that the mineral acids, Alum, and the salts of Iron, are the only astringents of this order which can in all cases be given internally with advantage. For being comparatively innocuous, they can be safely prescribed in the quantity required; whereas the other mineral Astringents are poisonous substances, which cannot be given in large doses without considerable danger.

Of the mineral acids, Sulphuric acid is the best Astringent. Phosphoric acid is seldom or never used as an Astringent. We might indeed have supposed it to be inapplicable, from the fact that it forms soluble compounds with albumen and fibrine,--instead of coagulating these substances, like the other mineral acids.

Sulphuric acid is a Restorative Hæmatic; and, when given in small doses, may remain in the blood, and not pass out through the glands. It acts first upon the mucous surface of the stomach. When there is a relaxation of this mucous membrane, as in many cases of atonic dyspepsia, with a large formation of flatus, and an over-secretion of the gastric fluid, this acid may be very serviceable. It tends to correct these evils by a topical action. In cases of Pyrosis, where there is an alkaline reaction in the vomited fluid, as sometimes occurs, Sulphuric acid is still more peculiarly applicable, because it further acts chemically in neutralizing this alkali. When given in large doses, the acid cannot remain in the system, but must be excreted from it by the glands. In passing through them it tends to act as an Astringent by corrugating and diminishing in caliber their minute ducts, and thus decreases the amount of the secretion. But it does not act on all glands alike. Dr. Bence Jones has found that it seldom passes out into the urine. It therefore does not sensibly diminish the secretion of urine. It is probably excreted partly by the skin, and partly by the bowels; for it diminishes the amount of the sweat in profuse perspiration, and of the fæces in diarrh[oe]a. Sulphuric acid is free before entrance into the blood, and after expulsion from it into the secretions. Thus at these periods it acts as an Astringent. But while in the blood it combines with the alkali contained in that fluid, and forms a salt which is not astringent. So that when it diminishes any secretion, this is nearly tantamount to a proof that it is actually excreted by the gland which forms that secretion. It acts on mucous membranes generally, being probably excreted in small quantities by those which are remote from the stomach. It is not of use in cases of hæmorrhage, except when the bleeding takes place from some mucous membrane. It is thus given with more or less advantage in Hæmatemesis, Hæmoptysis, Melæna, and chronic Dysentery--_i.e._ in hæmorrhage from the mucous surfaces of the lungs, stomach, and bowels.

Alum is a universal Astringent, acting more or less on all parts of the body, and diminishing all secretions. It is a very useful remedy in all cases where Astringents are required. It does not seem to be impaired in power while in the blood, as is the case with Sulphuric acid; and is therefore applicable in all hæmorrhagic cases. It has been highly recommended in the case of lead colic, and seems to operate in this instance by stimulating to contraction the muscular fibre of a paralyzed portion of the intestine.

The astringent salts of Iron are less active in this kind of influence than the medicines already referred to. They have very little action on the glands. But in cases of hæmorrhage they are particularly appropriate, for in addition to their astringent action they tend to restore the deficient red colouring matter of the blood. In many such instances the Sulphate or the Sesquichloride of Iron may be advantageously prescribed along with Sulphuric acid.

Acetate of Lead is used internally as an Astringent, but being a more dangerous remedy than the medicines above mentioned, it requires greater care in its application. It should not, if possible, be used long at a time. When it has been for some time prescribed, the blue line at the edge of the gums, which is characteristic of a saturation of the system by the poison of lead, will indicate that its further administration is unadvisable. The Acetate of Lead is much esteemed as an Astringent in the case of Hæmoptysis. It is frequently combined with Opium, in spite of the chemical decomposition which follows the admixture. But it must certainly not be prescribed with Alum.

The soluble salts of Silver, Zinc, and Copper, and the Bichloride of Mercury, are used with advantage as external Astringents, but can seldom be prescribed internally so as to act in this way, because they are poisonous when given in any quantity. The Sulphates of Zinc and Copper have, however, been occasionally used in diarrh[oe]a.

When thus applied as Astringents externally, their solutions must be very dilute, for all the mineral Astringents are caustic and corrosive, destroying texture, when in the solid state, or in strong solutions. These solutions may be applied to any part of the surface of the skin or mucous membrane, when relaxed, inflamed, or ulcerated. Their operation is simple and obvious. When one of them is applied to an inflamed eye, or to a red ulcerated sore, that is turgid with blood and discharges an unhealthy matter, it tends to promote the contraction of the dilated vessels, and thus dispels the congestion and diminishes the discharge.

Various other substances have wrongly obtained the title of Astringents, regard being had only to the result of their operation, and not to the mode in which it is produced. Thus Chalk is often of benefit in diarrh[oe]a. It acts both by mechanically absorbing irritating fluids, and protecting the surface of the bowel, and by chemically neutralizing an acid matter by which the irritation is maintained. And when applied to the surface of inflamed ulcerated parts, it does good by absorbing the discharge, and protecting from the contact of air. Thus its action in both cases is very different from that of the true Astringents.

The action of some of the minerals above named, when applied externally in the solid state, as caustics, must not be confounded with their astringent power. Its efficacy depends upon the revulsive effect which follows a local destruction of tissue.

ORD. II. VEGETABLE ASTRINGENTS.

(Tannic Acid. Gallic Acid. Kino; Catechu; Logwood; Oak-galls; Rhatany; Bistort; Pomegranate-rind; Rose-leaves; Uvæ Ursi; Tormentil. Creosote.)

Tannic Acid, Gallic Acid, and Creosote are the three chief Vegetable Astringents. To the first two the vegetable substances above enumerated appear to owe their efficacy. All contain Tannic Acid, or some modification of it; and Oak-galls contain also Gallic Acid.

The relative efficacy of these active principles may be summed up in a few words. Tannic and Gallic Acids may generally be used with great advantage in all cases in which Astringents are required. When applied externally, Tannic Acid is the most powerful; but for internal administration Gallic Acid is the best. The reason of this will presently appear. Creosote, being a powerful Neurotic, cannot be employed to act on distant parts, but is appropriate in cases of hæmorrhage from the surface of the stomach.

I have already said that I conceive the astringent powers of these substances to depend very much upon their chemical affinities. Tannic Acid precipitates both Albumen and Gelatine. Creosote also coagulates Albumen. But Gallic Acid does not affect either of them.

Tannic Acid does not seem to be a simple substance. When boiled with acids, or with alkalies, it yields Gallic Acid and a brown matter. Tannic and Gallic Acids yield the same set of products when submitted to destructive distillation. And it appears likely, from the researches of M. Braconnot, that Tannic is a compound acid consisting of Gallic Acid in combination with the elements of grape-sugar. Three atoms of Tannic Acid are together equivalent to six atoms of Gallic Acid and one of grape-sugar. When the solution of the former acid is heated in the air, or taken into the human system, the elements of grape-sugar are oxidized into Carbonic Acid and water, and Gallic Acid is set free. (_Vide_ Chap. IV. _Art. Tannic Acid_.)

It is thus Gallic Acid which passes out into the secretions, and exerts an astringent action at distant parts of the system. And as the Tannic Acid loses weight by the decomposition, it follows that a dose of Gallic Acid produces a greater effect as a medicine than an equal amount of the other. Thus one ascertained fact is cleared up by these chemical considerations, but other mysterious points remain still to be explained.

Gallic Acid does not precipitate albumen, and is of little use as an Astringent when applied to external parts; but it is very efficacious when given internally. Tannic Acid, which is equivalent in composition to a combination of Gallic Acid with a saccharine matter, is a valuable external Astringent. A further chemical discovery has been made, which appears to bear upon these facts. M. Pelletier has found that a mixture of a solution of Gallic Acid with one of Gum will precipitate albumen, although neither of them will affect it separately.[43]

Gum has the same composition as common sugar; and grape-sugar, or a material containing the same elements, is known to be continually forming in the blood. Thus it is likely that Gallic Acid may act along with this saccharine matter in the blood, and by this acquire chemically an astringent power, which it is not able to exert on external parts, because then isolated. But the saccharine matter is required in the system for special purposes, and thus Gallic Acid passes out into the secretions alone.

It seems probable, when Tannic Acid is given, that it is not decomposed into its constituent parts until it has to be separated from the blood by the glands.

These two compounds, and the vegetable substances that contain them, are used in diarrh[oe]a, and in all hæmorrhagic cases. To diminish sweating, Tannic is inferior to Sulphuric Acid; but to act as a remote Styptic, it is preferable to the other. Tannic and Gallic Acids diminish secretions generally; they are very useful in cases of hæmaturia, where Sulphuric Acid is all but useless.

Creosote is a Sedative, and cannot be well given in such large doses as to act upon distant parts. In cases of hæmatemesis it acts topically on the surface of the stomach in a double way, diminishing the hæmorrhage by its astringent power over the vessels, and quieting the nervous irritation by which the vascular excitement is often maintained. In cancerous cases the bleeding can never be permanently stopped.

This concludes the list of Astringent medicines.

Certain stimulant Eliminatives are employed for the purpose of checking mucous fluxes, and so far simulate the action of true Astringent medicines. Thus we administer, with more or less advantage, Aromatics in diarrh[oe]a; Cubebs, Copaiba, and Turpentine, in gonorrh[oe]a; and Balsam of Peru, and other oleo-resins, in Catarrhal affections. These medicines all act upon and pass through the glands of the several mucous surfaces which they affect: while so doing, they stimulate the healthy function and secretion of the gland, and cause it to displace the morbid one. Dr. Williams thinks that they first cause dilatation of the vessels of a gland, and that this is followed by contraction. There is no apparent reason why the latter effect should succeed the former. But supposing contraction to take place in this way, then these medicines would be true Astringents. But it cannot be so, for they do not diminish any of the natural secretions, but, on the contrary, increase them. Turpentine, Cubebs, and Copaiba, are Diuretics, and it is possible that while passing out in the urine they may simply stimulate the mucous surface of the inflamed urethra, and excite it to a healthy action.

These volatile oils are incapable of exerting a true astringent action. On the supposition that it is really an Astringent, Turpentine has been often prescribed as a remedy for hæmorrhages in different parts of the body. But it has very much disappointed the expectations that were entertained of its efficacy.

General Stimulants may act indirectly as styptics to a mucous surface, when relaxed and bleeding on account of an atonic condition of the nerves by which the contraction of the minute vessels is maintained.

Alcohol, in large quantity, coagulates albumen, and it may thus act as a true Astringent when applied externally.

Some Neurotic medicines diminish secretions in a way which is not well understood. The chief of these is Opium, which particularly diminishes the secretion of the bowels. Attempts have been made to explain this by an influence possessed by Morphia on the process of Endosmosis, but they are not satisfactory. Some little light may perhaps be thrown upon the matter by a consideration of the other operations of Opium; but it is difficult to explain it decisively in any way.

PROP. X.--_That a fourth class of medicines, called_ ELIMINATIVES, _act by passing out of the blood through the glands, which they excite to the performance of their functions_.

In this Fourth Class are included all the medicines which tend in a direct manner to increase secretion. They have received various appellations: some authors have called them special Stimulants; others, as Dr. Duncan, have named them Evacuants; while Dr. Pereira entitles them Eccritics.

The mode of operation of Eliminative medicines is a matter of considerable importance, and its consideration will require us first to make some inquiry into the character and functions of those important glandular organs which they are said to excite to action.

The rational explanation of the process of elimination or secretion has been in all ages of science a favourite topic for speculators and theorists,--sound or unsound in their views, according to the light that was given to them. With regard to its essential nature, and its immediate bearing on the cure of disease, the subject has been generally understood with tolerable clearness. From the time of Hippocrates downwards, the use of Evacuants in the treatment of fevers and other disorders has been recognised, and their efficacy usually explained by supposing that they caused the passage out of the body through the glands of certain matters that were formed in the blood, but ought not to remain in it.

This view was more particularly insisted on towards the close of the seventeenth century by Dr. Thomas Sydenham; and again at the commencement of the eighteenth by Dr. A. Pitcairn, in an Essay on the use of Evacuants in Fevers. These both had observed that fevers and other disorders had mostly a particular tendency to pass off with an increase in one or more of the secretions; and they drew from this, and from the results of their experience, that in stimulating and urging this secretion, the physician would be doing his best to promote a cure. (_Vide_ page 55.) More recently the same idea has been followed up by Cullen, Hamilton, and others.

This theory is not in our immediate province. Though based upon reasonable grounds, it has perhaps been too universally applied. It will suffice now if we assume that remedies whose action is to increase the amount of secretion have often an important bearing on the cure of disease. We have only to inquire into their manner of action. As a preliminary step, there is one general law of secretion which it is of importance that we should clearly lay down. It is this: it is the special office of each gland, or set of glands, to secrete from the blood particular materials, and to pass them out of the body.[44]

It follows from this law of selective secretion, that when any morbid substance or product,--or any thing which is in the system, but cannot naturally remain there,--has to pass out, it prefers to pass by some glands rather than by others. It must be remembered that the glands afford the only means by which a substance can make its exit from the blood. We are still much in the dark as to the _rationale_ of this force or attraction, by which particular matters are drawn towards each gland.

Dr. Pitcairn, a great man for the age in which he lived,--a man of original thought and natural genius,--gives us, in his Essay on the Circulation of the Blood, a learned account of three theories on this matter which were in vogue at his time. They are of importance, as showing that the fact was then very clearly recognised, however dubious the explanation of it might be. One party supposed that there was in each gland a certain material stored up, which prevented the passage through to itself of any substance that was not like it; just as when a sheet of paper is steeped in oil, oil only will pass through it, and not water. A second party, called the Chymical party, supposed that there must be in the immediate neighbourhood of each gland a subtle fluid or ferment, whose tendency and office it was to form and separate from the blood the materials which that gland had to secrete. A third set of physicians armed themselves with mathematics and with the newly discovered principles of Newton, and actually worked out formulæ and equations wherewith to support their arguments. They had strong and perhaps reasonable ideas as to the definite shapes of atoms. They averred that each gland was to be compared to a sieve or strainer, having in it pores of a particular size and certain geometrical shape, and that each secreted atom could only pass through a pore that would exactly coincide in size and figure with itself.

The first two of these theories Dr. Pitcairn disputed, and treated with high disdain. The third he accepted in a modified form. He supposed that the vessels in the glands ended in small open mouths, always circular, but differing in diameter in different glands, so that each would only admit the passage of a particle whose diameter approached a certain sum. Thus he supposed that each secretion would consist only of certain peculiar particles. Possibly Dr. Pitcairn forgot that small particles would seldom hesitate to pass through large holes.

We may perhaps feel inclined to make light of these crude speculations of the philosophers of the eighteenth century; we may be disposed to smile at the idea of vessels with open mouths, and of glands which are riddled with holes like the buckets of the Naiades; but we must after all confess that if at the present day we have swept away these notions, we have certainly added nothing in their stead, nor can we explain this matter at all more clearly than our predecessors a century and a half ago.

The fact, however, is plain, however vainly we may try to explain it. It is an established rule, to which there are few exceptions, that each substance which is formed in the blood and has to pass out of the body, tends to pass out through some particular glands; that it is the particular function of the kidneys to excrete water, urea, uric acid, and certain salts; that it is the especial office of the bowels to excrete certain effete matters and gases; and that it is the peculiar province of the liver to excrete fatty matters, taurine, cholesterine, and choleate of soda.

Water, being the necessary solvent of the solid matters in all the fluid secretions, is secreted in greater or less quantity by all the important glands. The kidneys are the chief emunctories of water,--_i.e._ they have to separate it from the blood when it has entered in an unnatural amount. But in the excretion of water there exists a compensating relation between the skin, kidneys, and bowels,--particularly between the two former. So that when water is not properly excreted by the kidneys, it may pass out by the skin, and _vice versâ_. It is well known that this change may be determined by several circumstances, particularly by the conditions of heat and cold, or moisture and dryness. The relation between the function of the skin and kidneys applies also to other fluid and solid substances, as will be seen when we consider the medicines which act upon these glands.

Now this law of selective secretion applies not only, as it seems to me, to substances which in the course of nature are formed in the blood, and have to be excreted from it, but also to other matters which have been, as it were, accidentally introduced from without, and which, being in the system, cannot properly remain there. Thus it would apply to all medicinal bodies which have passed from the stomach into the blood, and which, not being natural constituents of that fluid, must again pass out of it.

So that although it is often laid down that medicines acting on the glands do so simply by passing along in the blood, and stimulating them as they go by, I regard this as a needless complication of the subject, and a thing which is wholly without proof. In fine, I am brought to the opinion which I have laid down in the Tenth Proposition, and which I have now to establish as well as my space will permit. The affirmation may be thus divided into minor propositions:--

_m. p._ 1.--That Eliminatives are medicines which pass into the blood.

_m. p._ 2.--That they cannot remain there, but must pass out of the body.

_m. p._ 3.--That in so doing, they tend to pass out by some glands more than by others.

_m. p._ 4.--That the result of their passage through a gland is to increase its secretion.

_m. p._ 5.--That they are of use when the state of the system requires that the function of a gland should be restored or promoted.

What I wish to prove is, that a medicine increases secretion simply by being itself secreted; that while passing through a gland it stimulates the secreting cells, and rouses them to a proper performance of their natural function; that each eliminative medicine has a tendency towards particular glands, and increases the secretion of those glands; that thus, as far as our information on the subject extends, we find that Cathartics are excreted from the blood by the glands of the bowels, and pass out with the fæces; that Diuretics are to be discovered in the urine, Diaphoretics in the sweat, and those Expectorants which are volatile may be detected in the odour of the breath.

Any material which is naturally eliminated would act as an eliminative medicine. Thus if a drachm of Urea be dissolved in water, and injected into the veins of a dog, it causes copious urination, which continues until the whole is excreted. This well illustrates the argument.

Further, we find that when an eliminative medicine is diverted from the gland by which it usually passes out, it no longer augments the secretion of that gland. Dr. Ward gives an interesting case of a woman who was never purged by Castor-oil, but in whom the oil exuded from the skin, and acted as a Diaphoretic. And it is, as I have said, well known that the conditions of cold and exercise will cause a Diaphoretic, in most cases, to act on the kidneys, because it is then excreted by them. For the same reason, warmth, confinement, and rest, will induce a Diuretic medicine to act on the skin.

Thus if it be shown, on the one hand, that Eliminative medicines themselves pass through the glands whose secretions they augment; and, on the other hand, that when they do not pass through them, they do not, as a general rule, augment their secretion,--it may then fairly be presumed that they operate by so passing through.

I assert, then, that medicines which stimulate secretions are themselves secreted. But the converse of this--_i.e._ that all medicines which are secreted at the same time increase secretion,--though it holds good in the main, is not invariably true. There are two chief exceptions to it. These are Astringents and Hyperæmics.

When an Astringent passes through a gland, it tends, by its natural force, to decrease secretion, and to cause constriction of the ducts. Thus Uvæ Ursi may decrease the amount of the urine, although it sometimes does the opposite; in which case the eliminative may be said to surmount the astringent tendency. So also Catechu, Kino, and Sulphuric Acid, decrease the secretion of the intestinal glands. But general Astringents are not always glandular Astringents. Thus the mineral acids act as Diuretics.

By Hyperæmics I mean medicines which produce congestion. Powerful Eliminatives do this when given in excess, simply by exciting excessive action. Now it is a general rule that congestion, however caused, diminishes the secretion of a gland. Thus congestion of the liver produces jaundice; congestion of the kidney, ischuria. After scarlatina, when the kidneys are suddenly called upon to eliminate a morbid material from the blood, congestion of the glands may be caused: the urine is diminished, and dropsy results.

Cantharides and Turpentine are Diuretics. They increase the urine when taken in moderate doses; but when in an overdose, they diminish it, and may cause painful strangury, with an almost total suppression of the secretion. The explanation of such an action is obvious. Congestion is caused by the excessive action. In the same way we find that a large dose of Mercury, naturally a Cholagogue, may produce jaundice, by causing congestion of the liver. This fact has been observed by Dr. Graves, of Dublin.

In all cases, then, in which observations have been made, we find that an Eliminative medicine is secreted by the gland which is stimulated by it, and, in most cases, that a medicine which is excreted by a gland tends to increase its particular secretion.

Having made this general statement of the case, I must attempt a more particular and detailed proof. I will treat in turn of the above minor propositions, as applicable to the following orders of Eliminative medicines:--

CLASS IV. ELIMINANTIA.

Ord. 1. Sialagoga. Ord. 2. Expectorantia. Ord. 3. Cathartica. Ord. 4. Cholagoga. Ord. 5. Diaphoretica. Ord. 6. Diuretica.

They are enumerated nearly in the order of the glands, from above downwards, in the human body. I have not enumerated Errhines, because the medicines which are used to increase the nasal mucus are merely topical irritants, and not true Eliminatives.

Of Emetics I have already spoken. Some are Neurotics, acting from the blood on the nervous system; other are local irritants. They also are not true Eliminatives.

Neither are Emmenagogues so; for the uterus is not a gland. Some of these too are Neurotics. Most of them act by causing a determination of blood towards the organ. Cathartics do this by their action on the contiguous mucous membrane of the intestines. (_Vide_ page 102.)

These then are the six orders of Eliminative medicines. In the first minor proposition it is stated that they pass into the blood. This has already been in great part proved; for most Eliminative medicines belong also to one or more of the preceding classes, of which it has been shown that they pass into the blood.

Thus Antimony, Mercury, Acids, Alkalies, Sulphur, the Salts, etc., are Hæmatics primarily. The various volatile oils and resins are more or less Stimulants. So also Alcohol and Ether, as well as Camphor and others, are found among Narcotics. Colchicum, Digitalis, Creosote, and Ipecacuanha, are Sedatives. Many Eliminatives are certainly known to pass into the blood, because they are subsequently found in the secretions, as will be presently seen.

Secondly, these medicines cannot remain in the blood, but must sooner or later leave it. If they remained, they could not pass through the glandular cells. But if they pass out, they must inevitably be excreted by them.

All those medicines must be secreted which have nothing in the natural blood corresponding to them. This is the case with most Eliminatives, and with all medicines except the Restorative Hæmatics. And those Restoratives which act as Eliminatives, such as Acids and Alkalies, do so because they are introduced in so large a quantity that they cannot possibly remain in healthy blood. Thus all these medicines pass out through the glands.

Thirdly, we find that in so doing they tend to pass out by some particular glands rather than by others.

In order to show this we may consider first the chief tendencies of the great groups of Eliminative medicines; and secondly, I shall endeavour, when considering the six orders, to show that many of the medicines included in them have actually been found in the secretions of the glands towards which they tend. The first consideration will clear the way for the second. What we have to ascertain is, that the principle of selective secretion is generally applicable to Eliminative remedies.

The most important of the substances which are used to increase secretion may be divided chemically under the following six heads, of all of which it has been proved that they are capable of absorption. (Prop. II.)

1. Insoluble mineral substances. 2. Soluble minerals,--_i.e._ Acids, Alkalies, and Salts. 3. Ammonia and volatile oils. 4. Fixed acrid oils. 5. Resins and neutral acrid principles. 6. Soluble vegetable principles.

1. _Insoluble mineral substances._--The chief of these are Mercurials (Blue Pill and Calomel,) Iodine, and Sulphur. They are all more or less changed during the process of absorption, as they have to be reduced to a soluble condition. They stimulate secretion generally; but Mercury particularly tends to the liver, bowels, salivary glands, and skin; Iodine, to the kidneys, and to the salivary and mucous glands; Sulphur, to the skin.

2. _Soluble mineral substances._--Acids, Alkalies, and Salts, may pass off by any of the fluid secretions. The chief of these secretions are the sweat, the urine, and the secretion of the bowels. The sweat is only fluid when the skin is kept covered and very warm. In other cases the choice lies between the kidneys and the bowels. The kidneys are the grand purifiers of the blood, so that most of the substances which stimulate the other glands may occasionally pass off in the urine. And soluble minerals, which require some amount of water for proper solution, would tend for this reason towards the most fluid of the secretions.

But there are some other things which counter-balance this tendency. The constitution of the urine is such that it cannot safely be disturbed to a very great extent. If there be much excess in it either of acid or of alkali, a deposit is occasioned. Dr. Bence Jones found that Sulphuric acid never passed out in the urine in any quantity. We find too that when a certain quantity of a saline is administered, too great to pass off readily by the kidneys, it prefers to act on the bowels. It is more likely to be diuretic if much diluted with water; but this is not the only directing cause, for a very large quantity of a saline will prove purgative even when largely diluted. (_Vide_ Prop. II.) Thus the general rule is this: soluble minerals are in small doses Diuretic, in large quantity Purgative. This applies more especially to salts; for mineral acids act as astringents on the bowels,--and mineral alkalies, being corrosive, cannot be given in large doses.

3. _Ammonia and volatile oil._--The laws of endosmosis favour the passage of soluble substances through to a liquid secretion. They are dissolved and carried away on the other side of the membrane through which they pass. In the same way it appears that volatile substances may dissolve in, and be carried away by, air. Thus they have a tendency towards the aeriform secretions. These are,--the expired air, or the secretion of the air-cells of the lungs,--and the ordinary cutaneous transpiration. While passing through the air-cells, these matters stimulate the secretion of the lining mucous membrane. They cause a morbid secretion of this surface to be replaced by a more natural one. Thus Ammonia and volatile oils are Expectorant and Diaphoretic. They may all pass out in the urine, but do not especially tend to do so, with the exception of some that are acrid, and approach to the nature of the resinous group. Turpentine, Juniper, and Copaiba, are Diuretic.

4. _Acrid fixed oils._--Such are Castor and Croton Oils; they are Purgatives, passing off by the bowels.

5. _Resinous and neutral acrid principles._--These are soluble in alkalies, and thus partly absorbed in the intestinal canal. Most of them are Cathartic, whether introduced into the stomach or injected into the veins. Such are the resins of Scammony, Jalap, and Gamboge, and the principles of Colocynth and Elaterium. Some few of them are Diaphoretic, as Guaiacum and Mezereon. Some again are Diuretic, especially those which are liquid or associated with a volatile oil, which is the case with Copaiba, Cubebs, Cantharides, and others.

6. _Vegetable principles soluble in water._--Most of these are Diuretic; as are the Vegetable Acids, and the Alkaloids of Digitalis, Tobacco, and Colchicum. So also are the principles of Broom and Sarsaparilla. The Emetine in Ipecacuanha, and the Morphia in Opium, act on the skin. Aloesin, the principle of Aloes, is purgative. So is Cathartin, the soluble acrid principle of Senna.

Having thus briefly sketched out the particular tendencies in the operation of the groups of medicines which act on the glands, it remains for me to say that in very many cases these medicines have actually been proved to pass out of the body by the glands whose secretions they tend to increase. Whenever we are in a position to inquire into the facts by chemical or other means, we find that the Eliminative medicine is itself contained in the secretion which is augmented by its action, and that when the secretion upon which it usually acts is not augmented, the medicine has passed off by some other secretion instead. There are doubtless many cases in which no inquiry of the kind has been yet made; but it will be seen when we consider separately the Eliminative orders, that all that is known on the subject is in favour of the above statement.

Assuming, then, the third and fourth minor propositions together, we conclude that Eliminative medicines, which must pass out of the blood, tend to pass out by some glands more than by others, and that the result of their passage through a gland is to increase its secretion.

They do not exert a blood-influence, nor do they act on the nervous functions; but they operate on those obscure vital forces by which secretion is directed and controlled.

The fifth minor proposition treats of the application of these agents in the treatment of disease. They are of use when it is requisite that the function of a gland should be restored or promoted. There is scarcely any disease in which some or other of them may not be of service. Their remedial applications are many and important.

Eliminatives are used to restore the function of a gland when impaired. With this view, Cathartics are employed in constipation, Diaphoretics for dryness of skin, Cholagogues in torpid states of the liver.

They may eliminate a poison or morbid material, and thus resolve a disease. This probably is the rational explanation of the use of Diaphoretics and Diuretics in Fevers, Gout, and Rheumatism, and of purgative medicines in a great number of disorders.

We may, by an action on one gland, be enabled to replace the function of another gland. The amount of each secretion bears more or less an inverse proportion to that of other secretions. Thus when one of them is unduly copious, we may diminish it by stimulating the formation of another. In other cases the reverse condition may occur; one of the secretions may be diminished or suppressed by a cause over which we have no control, and the matters which should be contained in it may be left in the blood, causing various mischief there. Here again, by increasing one of the other secretions, we may replace the function of the diseased gland, and cause the elimination of these products from the body by another channel.

Fourthly, Eliminative medicines may be of service by draining away from the blood fluid and solid matters. The first result of their action is to stimulate the proper secretion of a gland; but when it is pushed to a further extent, they may actually case the excretion of some of the natural constituents of the blood. Thus by an action on the skin or the kidneys, we may cause a copious evacuation of water, holding in solution saline matters. By increasing the secretion of the intestinal glands, we may cause the albuminous serum of the blood to be poured out into the cavity of the bowels. Thus it is that all Eliminatives are more or less antiphlogistic. Cathartics are especially so. Their influence, when carried to excess, is analogous to that of blood-letting. As evacuants, Cathartics are employed in diseases of the brain especially; and Diuretics are made use of in dropsies to diminish the amount of fluid in the blood, and in this way to promote absorption.

So much having been said of the general action of Eliminatives, we proceed to make a few remarks on the individual orders of medicines which are included in this division. Those substances can alone be properly included in these groups which really act on the principle of elimination, as above defined. There are in many instances other medicines which are found to increase secretion in an indirect way.

ORD I. SIALAGOGUES.[45]

This name is applied to medicines which in various ways increase the quantity or promote the excretion of the saliva. They are seldom employed as remedial agents; for the excretion of saliva is constant and very rarely suppressed, and it is so small in quantity, and so great a source of inconvenience when increased to any amount, that Sialagogues can never be employed as general evacuants. There are two kinds of Sialagogues.

Any solid substance which excites the mucous surface of the mouth, as the natural food,--or even the act of mastication alone,--will suffice to bring on the secretion of saliva. An irritant substance, as Ginger, or Pyrethrum, tends especially to cause this secretion when masticated. Catechu and Betelleaf are chewed for this purpose by the natives of the East.

Such a stimulation of the salivary glands may be advantageously resorted to on the counter-irritant principle in obstinate cases of head-ache, ear-ache, or tooth-ache, or in neuralgic or chronic rheumatic affections of the face.

When the quantity of the saliva is thus increased, it should not be rejected, but always swallowed when possible; for this secretion is apparently useful in the stomach, and in some way essential to the proper carrying on of the digestive process. The chewing of Tobacco, Betel, and other substances, is frequently found useful by sailors on long voyages, and is adopted as a preservative against the dysentery and diarrh[oe]a with which they are so often affected. This advantage is to be attributed to the increase in the salivary secretion. On the other hand, we find that the practice of constant spitting is productive of very injurious effects; and it is more than possible that the pale faces, lank figures, and dyspeptic maladies, which are so common among the American people, may be due in part to the prevalence of this habit among them.

These topical irritants and masticatories are not true Eliminatives. There are also some medicines which by another topical action may occasionally produce salivation. These are Sedatives. Hydrocyanic acid, Digitalis, and nauseant medicines, may act locally so as to paralyze the muscular fibres by which the constriction of the salivary ducts is maintained, and thus allow the secretion to pour out uncontrolled into the cavity of the mouth.

_True or Eliminant Sialagogues._--These are medicines which are actually excreted from the blood by the salivary glands, and which increase their natural secretion while passing through them. Mercury is the most important of these. When given to a considerable extent, it causes soreness and redness of the gums, and profuse salivation. It probably increases the amount of saliva even before this soreness is produced. It is not given for the purpose of producing salivation, but in cases where the full action of Mercury is desired this symptom is made use of as a sign that the medicine has taken full effect upon the system. If we permit it to be carried to too great an extent, sloughing of the gums and other dangerous results may be produced.

In some rare cases salivation has followed the administration of Iodine. It is also not an unfrequent symptom of chronic poisoning by Lead. In cases of salivation by these Eliminative medicines, the substance which has caused the increased secretion may be, and has been, discovered in the saliva by chemical tests. They are therefore true Sialagogues.

ORD. II. EXPECTORANTS.

This term, when taken in its widest sense, is applied to all medicines that cause the evacuation of mucus from the secreting surface of the respiratory tubes and cavities. They help the natural process of Expectoration.

Many medicines are capable of acting indirectly as Expectorants. Any thing which causes cough, as an irritant gas, will do it. So will any thing that thins the mucus when thick and viscid,--_e.g._ the inspiration of the vapour of hot water. Special Sedatives, which control the function of the Vagus nerve, are especially notable as indirect Expectorants. Such are Antimony and Ipecacuanha. By diminishing the morbid irritability of the pulmonary surface, they prevent the continued secretion of mucus. By allaying a spasm of the small bronchial tubes, and controlling the nervous sensation of want of breath, they may promote the evacuation of that which is already secreted.

Opium and Stramonium, classed among Narcotics, depress the function of this nerve as well as the nervous forces generally. So do other medicines similar to them. Opium in small doses allays irritability and diminishes spasm, and is then an indirect Expectorant; but in large doses it acts so powerfully as to render respiration difficult and expectoration impossible. Its use therefore demands great caution.

_True Expectorants._--The action of Antimony and Ipecacuanha upon the secretion of bronchial mucus is of so specific a character as to render it highly probable that these medicines add to their neurotic influence a true eliminative agency. We are as yet unable to decide whether or not they are ever secreted by these mucous glands, because not only is the analysis of the mucus a matter of difficulty, but hitherto no investigation of the matter has been made. Squill also is probably an Eliminative Expectorant.

Many of the true Expectorants are volatile and odorous in nature. All excreted substances have to pass by an endosmotic process through a thin animal membrane. And it is necessary before they can pass, that there should be on the other side of this membrane something which is capable of dissolving them. Diuretics are soluble in water, and they pass through into a watery fluid. But these Expectorants, whether they pass through the mucous glands, or immediately through the thin wall of the lung-cell, are brought directly into contact with air. And in this air these volatile matters are soluble, and are carried away by it.

This appears to be the reason why the Eliminatives which are volatile in nature tend particularly to act on the two aeriform secretions,--_i.e._ on that of the air-cells of the lungs, and on the common cutaneous transpiration. For though the glands of the mucous membrane of the lungs secrete mucus, yet the chief object of the terminal portion of that membrane is to absorb and secrete the gaseous matters of the blood. The following are the chief volatile Expectorants, the odours of which have been clearly detected in the breath of persons to whom they have been administered:--Turpentine, Camphor, Alcohol, Ether, and the volatile oils of Onions, Fennel, Asaf[oe]tida, Carraway, Cinnamon, and Anise.

These medicines, and others like them, are thus excreted by the air-cells or mucous glands of the pulmonary surface, and while thus passing through they stimulate the latter to a right performance of their function. When, as in the case of Bronchitis, the secretion of mucus is increased in amount, or deteriorated into a purulent matter, they may be of service by causing the healthy secretion to replace the diseased one.

Expectorants are very uncertain agents. The reason of this is, that the pulmonary glands are not naturally intended to act as emunctories, or dischargers of morbid matters from the blood, and thus are less prone to be excited by Eliminative medicines than other glands whose proper office is one of general elimination. And yet we find that the effete gases which should be excreted by the bowels are sometimes voided by the lungs in case of aggravated dyspepsia, causing tainted breath. Just so may other adventitious elements of the blood, as these volatile medicines, be sometimes excreted by the pulmonary membrane. But they may often pass off by the skin or by the urine, and would not then act upon the lungs at all.

For the same reason that the lungs are not general emunctories, and cannot be made use of to produce a wholesale evacuation from the blood, Expectorants are of no use as general Antiphlogistics. In this they differ from the four remaining groups of Eliminatives.

They are only employed in pulmonary disorders, where we desire to influence the amount or character of the mucous secretion, when the mucous membrane is inflamed or irritated. In old and chronic cases of Bronchitis the stimulant volatile Expectorants are the most applicable. Tartar Emetic and Ipecacuanha are appropriate in acute and inflammatory cases, because they exert a nauseating and depressing action. They are sometimes given in sufficient dose to act as Emetics; for the act of vomiting mechanically assists the expulsion of mucus from the air-cells and passages by causing straining and compression of the lungs.

ORD. III. CATHARTICS.

Cathartics are medicines which tend to increase the secretion from the inner surface of the bowels, and promote the natural expulsion of the contents of the intestinal tube. Of these two operations the first only is an action of elimination, and the second is an accompaniment to it. The first can hardly take place without being followed by the second; but in some few cases the second action alone may be produced.

The subject of the application of Purgative medicines is so extensive, that it is impossible for us now to inquire into it at any great length. It should however be observed, that they are the most powerful and the most useful of all Eliminative medicines. The fæces consist partly of the undigested matters of the food, and partly of a secretion which is poured out by the inner surface of the bowel. (_Vide infra._) The majority of Cathartics increase this secretion. Whatever notion we may adopt as to its physiological purpose, it appears that we can act upon this intestinal function with ease and certainty in the great majority of cases. The surface of the intestine, covered as it is with a closely packed glandular apparatus, forms in the aggregate the largest secreting organ in the body. From the measurements made by Meckel, it appears that it covers a space of 1400 square inches. By the administration of a medicine of this sort, we are enabled to act upon this surface, producing simply an increase of the fæcal secretion, or causing, when the action is violent, an outpouring even of the fluid part of the blood. When this secretion is stopped, we may cause it to reappear; when another secretion is repressed, we may be enabled to replace it by this; and in the treatment of plethoric or inflammatory disorders, we find among Cathartics the simplest and readiest of antiphlogistic or evacuant medicines. For they possess these great advantages,--that they act with certainty, and produce a notable effect.

All medicines which by a mere external action augment the secretion of the bowels, or promote its evacuation, must be regarded as _indirect_ Cathartics, for they do not operate on the eliminative principle. An outward irritation of the mucous membrane is sufficient to excite the peristaltic contraction of the bowel, and may even increase the secretion of that mucous surface by a reflex nervous action, in the same way that an irritation of the mucous lining of the mouth will cause the secretion of the saliva. All substances which, after being taken into the stomach, are not absorbed, which are thus pushed onwards along the inner coat of the intestine, and by their mere accumulation excite its muscular contraction, must operate more or less as indirect purgatives. Of such a nature are the ligneous fibres of vegetables,--the bulky pulp of fruits, as in Prunes, Tamarinds, and Cassia,--and the husk of wheat in brown bread,--all of which are known to act as laxatives. Very different from these in the intensity of their action are the resinous Cathartics, as Scammony and Gamboge, which, though capable of absorption, appear also to act in some cases by an external irritation of the intestinal surface. They are also true Eliminatives, for they are known to become absorbed; they may thus act in a double way, both directly and indirectly. (_Vide_ p. 96.) In small doses it is probable that they are simply Eliminatives, but when given in large doses they may add to that an irritant external action, and produce a very powerful or even dangerous effect.

_True Cathartics._--These are very many in number. At whatever part of the system they are introduced, their action is the same. If one of them be injected in solution into the veins, or absorbed from the surface of the skin, it passes at length to the intestinal canal, is excreted by the glands of the mucous surface, and causes purging by augmenting their natural secretion. When given as a medicine, the Cathartic is first received into the stomach. It is capable of absorption,--whether it be soluble in water, or in acid, or be of an oily or resinous nature,--as was ascertained in the consideration of Proposition II. It is absorbed; and passes along in the circulation. But it is unnatural to the blood, and cannot remain in it; so that it is at length expelled by the eliminative force at the lower part of the intestinal canal, at a part which is more active in excretion than in absorption, though not very remote from the absorbent surface at which the remedy first entered.

Cathartics may be advantageously divided into three groups:--1. Mercurials, which tend to increase all secretions; 2. Some resins, oils, and acrid principles, which tend especially to the bowels; and 3. Salines, when given in such amount that they cannot pass off by the kidneys.

Mercurials, being also Cholagogues, are especially useful in bilious habits. When given to act on the bowels, a Mercurial is generally conjoined with another purgative, that it may not do damage in the system by remaining in the blood.

In the second group the great majority of Cathartics are included. They vary very much in the intensity of their action. Some are mild, and may be administered in inflammations and fevers, or even in pregnancy, where a gentle action is required; others are powerful and drastic, and may cause serious congestion, or even inflammation of the bowel. All the resins and acrid principles are more or less heating, and should be administered very carefully in febrile states of the system. Of the resins, Jalap is comparatively mild, and may be given to children without risk; while Scammony, Colocynth, and Gamboge are more drastic. Of the oils, Olive-oil is merely laxative; Castor-oil may be given in all cases without danger; but Croton oil is a dangerous hydragogue Cathartic. Of the medicines which owe their efficacy to acrid principles, there are some which are mild in operation, and whose principles are soluble in Water. Such are Rhubarb, Aloes, and Senna. Senna is somewhat irritant. Aloes appears to act on the lower part of the intestine, and is therefore objectionable in cases of pregnancy or of uterine disorder. Hellebore is a more powerful acrid, but is now seldom used. Elaterium is the most potent purgative known. In cases of dropsy, when all other medicines have failed, one-twelfth of a grain of this substance has been known to produce a copious evacuation.

Salines, _i.e._ salts of the alkaline and earthy metals, are all more or less purgative when given under certain conditions. Under other circumstances they may pass off from the body by the kidneys or the glands of the skin. The circumstances which determine the excretion of saline matters appear to be simple in nature. In the common condition of the body it is not possible for the secretion of the skin to be very largely increased, or rendered fluid. Suppose, then, a soluble saline, as the Sulphate of Soda or Magnesia, or Tartarized Soda, to have obtained entry into the blood, it has the choice of being excreted by the kidneys or the bowels. The alternative appears to depend mainly upon the amount of the dose. A small quantity may pass in the urine, and will not produce purging. But a large quantity cannot so pass; it is excreted by the glands of the bowels, and acts as a Purgative. It has been supposed by some that a saline solution proves Purgative or Diuretic according to the degree of its dilution only. This matter we have already considered at some length; and the reasons which have induced me to arrive at a contrary conclusion have been detailed under the head of Proposition II.

Salines are hydragogue. Requiring water for their proper solution, and having further a great affinity for it, they convey a large quantity of the aqueous part of the blood with them through the glands of the bowels. When their action is very powerful, some of the albumen of the blood may be purged away along with this. This may also take place with the drastic resinous Cathartics. But the latter are much more violent in their action, producing a degree of griping and irritation which is dangerous in febrile cases. Salines, on the contrary, are cooling, and mild in their operation. They are appropriate in inflammations, not only for this reason, but because, while passing through the blood, they exert in it, as we have already seen, a mild action of an antiphlogistic nature. (_Vide_ page 188.)

When the vegetable salts of the alkalies are given in diuretic doses they are decomposed into carbonates while in the system. This does not appear to be the case when they are given in such quantity as to pass off quickly by the bowels.

These various Cathartic medicines are affirmed to act on the eliminative principle: it follows then that they must themselves pass out of the body along with the secretion which is augmented by their action. It is natural that the fæces should have been less examined than other secretions. The resins of Jalap, Scammony, and other such substances, are affirmed to pass out along with them. Of the passage of saline Purgatives we have an indirect proof; which is, that after their administration the amount of saline matter in the urine is not materially increased. Castor-oil is seen in the evacuations, sometimes little altered, at other times in the form of a solid fatty substance. M. Lehmann has detected Mercury in the fæces, whenever it was given as a Purgative, and whatever the colour of the evacuation. When combined with a sufficient amount of Opium, it neither acts as a Purgative, nor does it pass out by the bowels; and it has therefore in that case a better opportunity of exerting its operation in the blood. We always find that when a Cathartic passes off in some other way than by the glands of the bowels, it fails to produce purging. Thus a copious dilution with water may sometimes cause it to be excreted by the kidneys, which are the natural emunctories of water. In some persons that are wont to perspire very freely it is difficult to produce purging. The case related by Dr. Ward of a woman with whom a dose of Castor-oil was seen to pass off by the skin, and invariably failed to act on the bowels, is an extreme instance of this kind.

Of what use and intention, we may now venture to ask, is this intestinal function, the continual maintenance of which in a healthy condition is found to be so essential?

It was some time ago supposed that the fæces consisted simply of those parts of the food which remained unabsorbed, and that all Purgative medicines alike acted by exciting the peristaltic motion of the bowels, and causing thus the ejection of these undigested matters. Such an opinion is now rarely maintained. Although very little is known of the separate functions of the glands of the intestinal mucous membrane, yet it is generally supposed that the fæcal matters consist in great part of excrementitious substances which are separated by their means from the blood. The excretion of fæces continues when no food is taken. It is known to go on with starving men, and with patients in fever. Liebig argues for the secretion of the greater part of the fæces, on the ground that they contain nitrogenous matters, whereas all the nitrogenous parts of the food should be absorbed for the purposes of nutrition. Thus these are probably the excreted products of changes in the system, which it is the province of the bowels to separate from the blood. (_Anim. Chem._ p. 156.) The odour of these matters is partly owing to sulphuretted hydrogen, or hydrosulphate of ammonia, both of which are the products of animal decomposition. On account of their presence a black colour is communicated to the fæces by the internal administration of the salts of Iron.

It seems to me to be probable that the constituents of the living as well as of the dead body are constantly subjected to the control of chemical laws, and undergoing destruction and change. Some products of these changes in an early stage are eliminated in the urine; but in great part they go on to actual putrefaction. The products of this, which are of an offensive character, are apparently discharged from the body through the follicles and glands of the intestines. We find that this decomposition is promoted and accelerated by heat, in the same way as with dead animal matter. For this reason it appears that the natives of warm climates excrete a much larger quantity of fæces than the dwellers in colder latitudes; and they are also more subject to Dysentery, Diarrh[oe]a, and Cholera, on account of the extra work thrown upon their intestines. A similar explanation may perhaps be assigned to a curious fact noticed some time ago by Mr. Curling--viz., that acute ulceration of the duodenum is a frequent consequence of severe superficial burns. A quantity of gangrenous or decomposing matter may in such a case be carried from the surface into the circulation.

This blood-decomposition, which I suppose to be always going on, may be accelerated by the action of certain morbid poisons or processes. The secretion of the bowels is then increased, and by the excitement or over-work a diseased condition of the intestinal surface may be established. In this way the diarrh[oe]a and ulceration of the glands in Typhoid fever may be accounted for. The air of a dissecting-room, or the neighbourhood of a noxious sewer, is apt to bring on diarrh[oe]a by exciting a putrefaction of the blood. Severe bodily exercise, as a long walk, may cause it, by increasing the waste of tissue. We find that constipation is commonest in youth, when nutrition is most active; and diarrh[oe]a most frequent in old age, when waste and decay go on the fastest.

When these decomposed matters which should be excreted, are retained in the blood, as is the case in constipation, they affect very injuriously both the brain and the system in general, causing torpidity of the one, and in the other favouring the progress and development of every description of morbid action. It is by cleaning such matters out of the blood, as well as by their antiphlogistic or evacuant action, that Cathartics become useful in so many diseases, and particularly in disorders of the brain. It would seem that the substances which would be eliminated by the bowels have, when retained in the blood, a peculiar action in the aggravation of disorders of this latter organ. Thus from very early times the exhibition of drastic purgatives, particularly Hellebore, has been strongly recommended in cases of mania.

But there is scarcely any disorder in which there is not, in some way or other, a deranged condition of the intestinal function, and in which, therefore, the judicious employment of purgative medicines is not at some time necessary. Either there is constipation, in which case there is a danger of the fæcal matters being retained in the blood; or there is diarrh[oe]a, which is probably due to an over-formation of these materials in the system, and an attempt of nature at their evacuation. In each of these cases Cathartics may be necessary. The first condition is the more obstinate of the two; the second the more immediately dangerous. Some general indications for their treatment may be alluded to.

In the treatment of constipated habits it is better to keep up a constant and gentle action on the bowels than to give violent doses occasionally. A condition of this sort may sometimes co-exist with comparative health, and may then often be remedied by a slight alteration in diet, and the prescription of such kinds of food as are more relaxing in their nature than those hitherto taken. Dr. Hamilton, in his work on Purgative Medicines, states that when they are given in constipation he has found that they become more and more powerful, and may be taken in smaller and smaller doses the longer they are continued. This is probably the case with such as Castor-oil, Scammony, and Jalap, which are simply cathartic in their action. But others, such as Rhubarb and Aloes, contain a bitter and astringent matter along with the purgative principle, and though they first act upon the bowels tend for this reason in the second place to confine them. Thus while the former are best in cases of constipation, the latter are preferable in diarrh[oe]a, as they supply us then with the very action which we require.

There are two ways, apparently opposite and inconsistent, of treating a flux from the bowels. We may try to encourage it by Purgatives; or attempt to suppress it by Astringents. Thus we may treat a common diarrh[oe]a by Castor-oil, or by Sulphuric Acid. In dysentery we may give Calomel, or Catechu. Even in Cholera some recommend Opium, while others have employed Croton-oil. In the most obvious case, _i.e._ in simple diarrh[oe]a, it is apparent that both plans are appropriate, but at different periods of the disorder. The symptom depends upon the fact of something being formed in the blood which ought to be excreted from it. Probably it is an excess of that material which is ordinarily excreted by the bowels. Its passage out by a natural effort causes at first a simple increase of the usual evacuation. It is at this time that we should give a Purgative, to favour the natural excretion, and thus, if possible, to put an end to the disturbance. But sometimes it fails to do so. The matters to be excreted are irritating, and such an excitement may be caused in the glands by their passage out, that even after this necessary secretion an inordinate and unnatural flux may be maintained. When the symptom is thus inveterate, and refuses to yield to a brisk Cathartic, it is advisable to resort to Astringents, in order to put a speedy stop to the too copious secretion. To do this in the first instance would have been wrong, except in special instances,--as in the diarrh[oe]a which is the forerunner of cholera, when Astringents should be used from the first.

In some febrile and plethoric cases it is difficult to obtain the full action of a Purgative. This is because the absorption of the medicine is prevented by the pressure on the vascular system, and without this absorption the proper action of the Purgative cannot take place, for it has no opportunity of passing out of the blood through the glands of the bowels. In such instances it is well to combine the Cathartic with a small dose of Tartar Emetic or Ipecacuanha, which by its nauseant operation may diminish the vascular pressure, and thus favour the necessary absorption. The action of a Cathartic itself favours absorption, by draining away the fluid part of the blood, and so diminishing the tenseness of the vessels.

ORD. IV. CHOLAGOQUES.

Medicines which are thought to stimulate the action of the liver, and to promote the excretion of bile, are called Cholagogues.

There is no doubt that the function of the liver, regarded simply as a gland, is of great importance in the animal economy. We know that certain matters are excreted from the system by that organ, which, when allowed to remain in the blood, as in the case of jaundice, are found to be hurtful. Also it appears that certain other parts of the bile are secreted or formed by the same gland, for the purpose of being re-absorbed into the blood from the intestine, and that they serve some useful purpose in the processes which go on in the circulation. (_Vide_ p. 137.)

A disorder of the liver by itself, _i.e._ unassociated with diseases of other organs, is comparatively uncommon. A failure in the secretion of bile is evidenced more or less by the well known icteric symptoms. Jaundice is often caused by an obstruction in the hepatic ducts. In such cases it is worse than useless to urge the liver to an extra formation of a secretion which can find no outlet. But other cases, in which the discoloration of the skin is in general incomplete, may be due to torpidity, congestion, or chronic inflammation of the organ. In such instances Cholagogues may be cautiously used; but when there is acute inflammation they may do harm; and when there is a probability of structural change in the liver, they may be useless.

The great majority of intestinal diseases, as also of chronic blood-disorders, are associated with a torpidity or derangement of the function of the liver. We find this to be the case with diarrh[oe]a and constipation, with dysentery and cholera; as well as with ague and remittents,--gout, and rheumatism,--Phthisis, and scrofula. In all of these diseases it is of great importance to attend to the state of the liver. I have already stated that Quina and other Tonics are of very particular use in such cases of disorder of the hepatic functions, and have attempted to discover an explanation of this fact (p. 142.) But we are at present concerned with medicines which tend immediately to increase the secretion of bile. They are more or less applicable in all the disorders which have just been enumerated. All Cathartic medicines act as indirect Cholagogues. This is particularly the case with the drastic purgatives. There appears to be a vital connexion between the action of the intestinal canal and that of the liver, so that any process going on in the one will excite the function of the other. Thus the bile is poured out during the process of digestion; and the peristaltic motion and extra-secretion, produced in the bowel by the action of a purge, causes likewise a sympathetic formation and excretion of bile. It is supposed by some that this result is due to an irritation of the orifice of the hepatic duct in the duodenum, produced by the purgative medicine. We must either suppose the stimulus of the food, which produces the same effect, to operate in the same way,--or reject such an explanation as superfluous, which appears to me the better alternative. For it is probable that the action of a Purgative is not at all exerted in the duodenum, but that it is actually absorbed there, and works out its operation in the lower part of the small and in the large intestine.

_True Cholagogues._--We are not well informed as to the exact number of medicines which pass out into the secretion of bile, and act thus on the true eliminative plan. But there is no medicine which is of such great and universal utility in all liver diseases as Mercury,--in its various forms. Mercurials increase more or less all secretions; and even if we had no direct proof of their action on the liver, we might almost have affirmed that they especially increased the secretion of bile, from the obvious way in which bilious symptoms yield to their action. But we have a direct proof of this. M. Buchheim has made some careful experiments on a dog. Having given it Mercury, he cut down upon the hepatic duct, observed and collected the secretion, and subsequently analyzed it. He found that the bile was increased, and that Mercury was contained in it. (_Vide_ p. 275.) Certain other purgative medicines are popularly, and perhaps correctly, esteemed as specific Cholagogues. These are Rhubarb and Aloes. Taraxacum is also thought to act upon the liver. But of the true eliminative action of these medicines we have no proof.

It is probable that alkalies and fatty matters may act in certain cases as true Cholagogues, for they are both contained in the natural secretion of bile, and therefore likely to pass into it.

In many cases of debility, and even of Scrofula, small doses of Mercury may act efficiently as tonics, by stimulating the function of the liver, which in such instances is generally deranged.

ORD. V. DIAPHORETICS.

These are medicines which tend to promote the secretion and exhalation from the surface of the skin. Of the matters which are given off from the surface of the body there are three kinds. Water in the state of insensible vapour, and volatile matters, are continually exhaling from the skin at all points, and pass unnoticed into the atmosphere around. The liquid sweat, which in the ordinary state of the body is only given off in sufficient amount to prevent the skin from becoming over-dry, is secreted by the sudoriferous glands, whose ducts terminate in large numbers on the surface at every part. There is in the third place an oily material, formed for a similar purpose by the sebaceous glands, which are widely distributed, but fewer in number than the last. Diaphoretics seem to increase only the first two kinds, viz., the aeriform transpiration, and the liquid sweat; and they act upon these in a varying proportion. In the consideration of this order we have not only to bear in mind the distinction between these two kinds of diaphoresis, but to note further the important relations existing between the action of these medicines and the state of the atmosphere, the condition of the body, and amount of other secretions.

In all relaxed conditions of the general system, the amount of the perspiration is apt to be increased. This is especially evident in the weakness which follows a paroxysm of simple fever. The force of the heart is weakened, the tone of the capillaries impaired,--and by these conditions absorption is favoured, and the amount of fluid in the blood increased. At the same time the muscular system is relaxed, and the sudoriferous ducts being thrown open by the diminished contraction of the involuntary fibre that surrounds them, the excretion of the sweat is favoured, and the watery parts of the blood are poured out through the skin. This general relaxation precedes and follows the act of vomiting, as induced by a dose of Tartar Emetic or Ipecacuanha. Thus these medicines act indirectly as Diaphoretics, when given in emetic doses.

_True Diaphoretics._--The following groups of medicines may be briefly noticed as tending to act as Eliminatives on the glands of the skin. Five divisions may be made:--1. Salines and diluents, under certain conditions; 2. Volatile substances which are soluble in air, as Ammonia, volatile oils, and Alcohol; 3. Certain acrid matters, as Guaiacum; 4. Certain Narcotics, as Opium and Camphor; 5. Antimony, Mercury, and Sulphur.

These Diaphoretics are all more or less uncertain in their action, as we have seen to be the case with Expectorants. There are two causes of this uncertainty. In the first place, the secretion of sweat, like that of the lungs, cannot be considered as a common emunctory. There are hardly any solid matters in it which are not also contained in the urine, and commonly excreted by the kidneys. It is only in special cases, or when there is a fault in the normal formation of urine, that the skin is called upon to eliminate materials from the blood.

In the second place, there are certain atmospheric and other conditions which promote the secretion of sweat, and certain others of an opposite nature which tend to retard it, and to divert into another channel the aqueous materials which should pass into it. With regard to the state of the atmosphere, warmth favours diaphoresis, cold repels it. Warm dry air, especially when in motion, promotes the aeriform transpiration, by favouring evaporation. Moist air, which hinders evaporation, promotes liquid sweating. Very active exercise, with the surface warmly clad, produces liquid perspiration. Moderate exercise, with a cool surface, favours diuresis. The recumbent posture, and sleep, promote diaphoresis; the erect posture and wakefulness, diuresis. Thus when it is required to produce sweating, the patient is ordered to lie in bed, to be covered warmly, and to compose himself to sleep. Any thing which keeps the surface of the skin unnaturally warm, as a hot-air or hot-vapour bath,--or thick flannel clothing, which is a non-conductor of heat,--tends powerfully to cause diaphoresis. So does friction, which stimulates and dilates the external capillaries.

So far the conditions of sweating and of diuresis are nearly opposite. But this is not the case with the medicines which are used to cause them.

Diluents, and salines soluble in water, form the first group of true Diaphoretics. Water promotes alike the function of the skin and of the kidneys; and it is only by a regulation of the circumstances mentioned above that it can be diverted from the latter towards the former. Diluent drinks are indispensable adjuncts to a Diaphoretic regimen. Salines also tend naturally to pass off in the urine, when in small doses; but when in large amount, by the bowels. A saline, being soluble in water, cannot pass out except into a fluid secretion; so that a saline diaphoretic should be given in a moderate dose, and to secure its action the skin should be kept covered and warm, and the patient in a recumbent posture. The medicine will then pass off into the liquid sweat, as it otherwise would have passed into the urine.

Volatile Diaphoretics may increase the cutaneous transpiration, and pass off by the skin, without the production of sensible liquid sweating. For being soluble in air, and capable of being carried away by it, they therefore tend especially to the two aeriform secretions, _i.e._ those of the lungs and of the cutaneous surface. (_Vide_ pp. 278, 285.) Ammonia and its various salts are very useful as Diaphoretics. Volatile oils are less energetic, for they often pass off with such ease as not sensibly to increase the secretion of the skin.

Some acrid matters, as Guaiacum, Mezereon, and Senega, appear to act specifically on the function of the skin. So also do certain Narcotics, among which Opium is conspicuous as the most certain Diaphoretic that we possess, though its other operations prevent it from being applicable in all cases.

Antimony, Mercury, and Sulphur, are medicines which appear to a greater or less degree to increase all the secretions in the body. When given in the insoluble form, they are reduced by the system to a soluble state. When Tartar Emetic is given in small doses, its only apparent action is slightly to increase the perspiration. It is probable that it then passes out through the glands of the skin. When given in emetic doses, it may produce sweating indirectly, as mentioned above. Iodine, which also increases secretion generally, acts sometimes as a Diaphoretic.

Many volatile oils have been detected by their odour in the perspiration, as those of Garlic, Onion, Asaf[oe]tida, Musk, and Copaiba. Mercury, Sulphur, and Iodine, have been detected chemically in it. It has happened, when a course of Mercury has followed the administration of Sulphur, that parts of the skin have turned black, from the formation of Sulphuret of Mercury. So it is proved of many of these Diaphoretics, and thus rendered highly probable of the rest, that they are true Eliminatives, being themselves excreted by the glands which they excite to action.

When copious diaphoresis has been excited, care should be taken that it be allowed to subside gradually, or the consequences may be hurtful. It may be remarked that cleanliness of the surface, by which the sudoriferous ducts are kept open and healthy, is highly important to the proper function of the skin.

Diaphoretics are useful in various disorders. In what is called _a cold_, when the function of the skin has been suddenly interfered with, and the vaporous transpiration is all thrown upon the lungs, producing irritation or inflammation of the respiratory mucous surface, Diaphoretics are generally required. In Fevers, and some other disorders, as Gout and Rheumatism, which are apt to improve or to pass off with an increase of perspiration, and in which it often seems likely that some morbid material may be eliminated by this channel, the same medicines are constantly necessary. When another secretion is unduly copious, an increase in the sweat may cause it to diminish. Thus in some cases of diarrh[oe]a, and still more in diabetes, Diaphoretics are appropriate. In contrary conditions, as when the formation of urine is unnaturally small, on account of granular degeneration of the kidney, it is again important to stimulate the secretion of the skin, that it may, if possible, be able to replace the other. (_Vide_ p. 280.)

ORD. VI. DIURETICS.

These are medicines which tend to increase the secretion of urine.

By means of the kidneys a large amount of aqueous material is every day separated from the blood, and excreted. This water is in the first instance absorbed by the surface of the stomach and intestine. The causes which demand its excretion are twofold. In the first place, it is necessary that the blood should be kept down to its normal standard as regards water, and that the surplus fluid which is daily added to it should be removed. Secondly, this water is required in the urine as a vehicle, to hold in solution there certain soluble matters which are continually forming in the blood, or being received into it, but which have to be excreted from it by means of the kidneys. These matters comprehend a variety of salts,--and a number of nitrogenous substances, of which the best-known are urea and uric acid. These last are formed in the blood by the gradual decomposition or change of the animal tissues through which it flows. When retained in the circulation, on account of a failure of the function of the kidneys, they act as poisons.

The kidneys are the chief emunctories of water; and mineral substances which are soluble in water tend for this reason to pass out into the urine. Many of these, as the salts of Iron, Silver, Lead, and Copper, are Astringents, and tend to diminish rather than to increase the amount of urine. But the urine is so necessary and so constant a secretion, that it is very difficult to diminish it in quantity. Saline medicines act as Diuretics under certain conditions. So also do acids and alkalies, and many vegetable substances, which will be presently spoken of.

The soluble substances which thus pass off in the urine, and act as Diuretics, are many in number, but they are all uncertain in action, for several reasons. The amount of the urine depends very much on the quantity of water taken into the stomach, or absorbed from the atmosphere through the skin; so that when there is not a sufficient quantity of water in the system, it is impossible for more urine to be formed. This necessary absorption of water depends again upon the pressure of the circulation; when this is too great, it cannot go on, and the urine is diminished. A large increase in any other of the secretions, as that of the bowels,--but particularly of the skin, as in warm dry weather,--hinders diuresis. The secretion of the urine is favoured by those conditions which repress the perspiration; as by coldness of the surface, light clothing, a cold and damp condition of the atmosphere, and the erect posture. In the fourth place, the urine is diminished by causes which impede the circulation, as by congestion of the kidney or liver,--or of the whole venous system, on account of obstruction in the heart,--conditions which produce dropsy.

Those medicines act as indirect Diuretics, which, by favouring the removal of one of these hindering causes, tend to allow the secretion of urine to go on as in health. The powerful action of the heart in fevers and inflammations causes such a pressure on the vessels as to retard absorption, and thus hinders diuresis. A hard bounding pulse and hot skin favour sweating more than diuresis, though they often diminish both of these secretions. Both are assisted by a relaxed state of the circulation, which favours the absorption of fluids. Thus venesection, purging, Antimony, or any thing that diminishes a febrile reaction, will help diuresis in such cases. In cases of congestion on account of cardiac disease, Digitalis, which, by powerfully weakening the force of the heart, both diminishes congestion and favours absorption, is a most efficient promoter of the natural function of the kidneys. When the portal circulation is the seat of the obstruction, a mercurial, such as blue pill, which especially acts on the liver, will be a most desirable adjunct to the other remedies employed. Tobacco and Lobelia, like Digitalis, promote diuresis by diminishing the force of the heart.

_True Diuretics._--Though all true Diuretics pass into the urine, the converse of this, _i.e._ that all matters which pass into the urine are Diuretic, is not always true. Thus the astringent mineral salts pass frequently out of the system in the urine, but seldom affect its amount in either way. And for the reasons already enumerated, it is often impossible, even by the most powerful medicines of this order, to increase the urine beyond a certain amount.

Diuretics may be somewhat loosely arranged in four groups:--1. Water, and soluble mineral substances, _i.e._ acids, alkalies, and salines under certain conditions; 2. Acrid matters of various kinds; 3. Alcoholic and ethereal liquids; 4. The minerals which increase all secretions.

Diluents promote the secretions of the skin and kidneys. A certain quantity of water must be given with every diuretic dose, and the larger the quantity the greater will be the effect produced. In the case of a Diaphoretic, this is all that is required. But as Diuretics are generally given, as in dropsies, for the purpose of eliminating fluid out of the system, this object would be clearly defeated by the introduction of a large quantity of water into the system. This, therefore, should be avoided. The free acids, both mineral and vegetable, with the exception of Sulphuric acid (_vide_ p. 262,) pass into the urine, and act as Diuretics. So also do the mineral alkalies. But as these medicines have important agencies in the blood, and tend further, by altering the reaction of the urine, to produce in it deposits of different kinds (_vide_ p. 151,) they can seldom be safely employed for this purpose. Salines are more appropriate. They should not be given in large doses, for they will then act upon the bowels. The dose should be small, and moderately diluted with water. To prevent it from acting upon the skin, the conditions which favour diaphoresis should be, if possible, avoided. The subject of the action of saline medicines, and the effect of dilution upon this action, has been already considered. (p. 74.)

The acrid Diuretics are perhaps the most powerful medicines in the order. One of them, Cantharides, is an animal product. Some contain or consist of volatile oils: as Juniper, Turpentine, Cajeput, Copaiba, Horseradish. These volatile oils may act upon the skin instead of the kidneys, under the conditions which are mentioned above as favouring diaphoresis. Others of this group contain peculiar vegetable principles; as Broom, Chimaphila, Taraxacum, Colchicum, and Squill.

Alcohol, Ether, and Nitric ether, act powerfully both on the kidneys and on the skin. Wine, which further contains certain volatile oils, and sometimes a vegetable acid, acts on the kidneys when drunk in any quantity. The diuretic effect of these liquids is, as in the case of salines, greater when the surface is cold, and less when it is warm and covered.

Mercury, Antimony, and Iodine, which increase more or less all the animal secretions, act, among others, upon the secretion of urine. Iodine particularly is said to be diuretic. Mercury and Antimony are most efficacious as indirect agents; the former by stimulating the function of the liver when impaired, the other by diminishing the pressure on the vessels in febrile cases.

A large number of Diuretics are themselves secreted by the kidneys, and have been proved to pass out into the urine. A great many have been detected in the urine by different chemists, especially by M. Wöhler. The Carbonate, Nitrate, and Chlorate of Potash, and the Iodide of Potassium, have been found there. So also have the mineral acids--the vegetable acids--Magnesia--Mercury,[46] in combination--and Iodine, in the form of Hydriotic acid. Among vegetables, the principles of Chimaphila and Uvæ Ursi--the oils of Turpentine and Juniper, somewhat altered in nature--the oil and resin of Copaiba--and the acrid principle of Cubebs, all pass into it. Other substances, which are not diuretic, but astringent, have been found in the urine; as Alum, Lead, and the Morphia and Meconic acid of Opium.

When a powerful Diuretic is given in too large a dose, it may cause a degree of action sufficient to produce congestion of the kidney, and so defeat the object for which it was intended. For congestion of a gland is invariably followed by a diminution or stoppage of its secretion. So a large dose of Turpentine or Cantharides may cause a dangerous attack of strangury, or even a total suppression of the urine for a time. (_Vide_ p. 274.)

It can hardly be said that Diuretics are of very extensive application in the treatment of disease, or that they are medicines which can ever be much relied upon. For not only are the remedies themselves uncertain in action, but it happens also that the disorders in which they are most required are of a peculiarly obstinate nature.

There are two chief actions for which Diuretics may be required. They may be used: (1.) to eliminate solid materials from the blood; (2.) to promote absorption, by diminishing the amount of fluid in the blood. It is easier to employ the first than to exert the second of these operations.

When there is habitually a deposit in the urine, of lithates, or phosphates, or other solid matters, the simplest mode of obtaining a solution of this deposit, and thus preventing dangerous consequences, is to increase the amount of the fluid part of the secretion. Water is the best medicine for this purpose, and all Diuretics that are given with such an object should be freely diluted with water. In Gout and Rheumatism, remedies of this order may be of service by promoting the excretion from the blood of the uric or lactic acid formed there. They may also be used as Eliminatives in fevers and other disorders. In the strangury which may sometimes follow the application of a blister to the skin, copious draughts of water are often prescribed with advantage, for they serve to wash out of the blood the acrid matter which has been absorbed from the surface.

It is for the second purpose, in cases of dropsy, produced by congestion of the liver, kidneys, or general circulation, that Diuretics are most urgently required, but are least efficacious. This congestion or pressure on the veins diminishes the amount of the secretion of urine, and by so doing increases itself, and aggravates the effusion and disorder. The same cause most effectually hinders the action of a Diuretic. If only we could largely increase the secretion of urine, the pressure on the venous system would be diminished, and absorption of the effused fluids might take place. In some cases of dropsy caused by renal congestion, the attempt is so hopeless that it is better to resort to Diaphoretics. In obstruction on account of heart disease, or congestion of the liver, we may sometimes gain our point by combining other Diuretics with Digitalis or Blue-pill, remedies which tend to remove the causes by which the diuretic action is hindered. (_Vide_ p. 304.) Even then we can often produce a much more copious and effectual drain of fluid from the blood by an action on the bowels, as by a dose of Jalap or Elaterium. When a Diuretic is required to eliminate fluid from the system, the dose should not be much diluted with water; this should only be done when we desire to eliminate solids from the blood. It is often advisable to combine together a number of different Diuretics, in the same prescription, so that by their joint but various agencies the causes which hinder their action may be overcome. The operation of Diaphoretics is opposed to that of Diuretics, but it is not always so with purgative medicines. The urine is often increased by the action of a hydragogue Cathartic; and a combination of Blue-pill and Squill supplies us with one of the best of known Diuretics. It is applicable in cardiac dropsy as well as in hepatic cases.

Thus is concluded a brief outline of the actions and uses of the six orders of Eliminative medicines.