part i. p. 126.) A supply of oil might then serve to restore this fat,

and afford a sufficient pabulum to the devouring element.

Thus an attention to diet is of great importance in the cure and alleviation of different diseases; for by this means we are enabled, within a certain limit, to regulate and control the composition of the blood, and through it the nutrition of the body.

Thus are Aliments essentially Restorative, forming and supplying the blood, and from it the several tissues, which are destined to work and to endure, until, like all organic creations, their turn is come to die. Then only are they excreted, and in a different form from that in which they entered; at that time, developing into tissues of high organization, they now decompose and retrograde into simpler bodies; at first fitted for life, they are now shaping for destruction. The disease which collectively they are intended to cure is Hunger; which is in fact a call from the blood for the renovation of its failing constituents, a demand for fresh supply from the body, which, because always changing, is always requiring nutriment.

ORD. II. ACIDS.

(_Mineral:_--Sulphuric, Hydrochloric, Nitric, and Phosphoric Acids. _Vegetable:_--Acetic, Citric, Tartaric, and Malic Acids.)

To this list may be added the super-salts of the alkalies, which have an acid reaction.

Although the mineral differ from the vegetable acids in their ultimate action, and are altogether more powerful than them, yet in their proximate effects they are similar. They are all soluble in water, and, when given as medicines, should be so diluted that they can exert no corrosive action on the mucous coat of the stomach and intestines.

Dr. Pereira lays it down as an axiom that though they all act as acids in the alimentary canal, yet that they enter the blood as salts. He considers that they combine with free alkaline matters in the saliva, bile, and Pancreatic juice. (_Materia Medica_, vol. i. p. 171.)

But this explanation seems to me to be calculated to communicate an erroneous idea of their action. For supposing first that they did thus combine with alkalies before entering the blood, yet as more alkaline matter would then have to be secreted to supply that which they had neutralized, they would thus immediately increase the amount of acid in that fluid. The action of acids in the blood is very different from that of their salts. Sulphuric acid does not act like the sulphates of Soda and Magnesia, nor is the action of Hydrochloric acid the same as that of common salt. Again, we must remember that the secretions mentioned are either neutral or barely alkaline in their reaction, and that the acid medicine, on passing into the stomach, would meet there with an active absorbent surface, secreting an acid, and not an alkaline fluid. So that it seems probable that the acid would enter the blood as such.

Now the presence of the acid is not unnatural to the blood. The mineral acids exist there in combination, and the vegetable acids have an analogue in lactic acid.

The blood is alkaline; which is due either to the presence of carbonate of Soda, or (according to Liebig) of an alkaline phosphate of that base. So that the acid, on entering into the blood, passes at once into combination with this alkali, and the result of this is a general diminution of the amount of basic matter in the system, and an increase in that of acid. Thus a free acid may act as a Restorative in cases where there is an excess of alkali in the blood. It may either remain in the blood after entering into combination, or it may pass off by the urine, supplying there the place of a natural acid, which it leaves behind it in the system. It is on such a theory as this that the action of mineral acids in typhoid and putrid fevers has been explained. I do not mean to affirm positively that there is in these cases an excess of alkali in the blood. Although likely, it is not proved. The explanation is plausible.

Acids are used to correct a phosphatic deposit in the urine, caused by an alkalinity of that secretion. The alkaline urine may be secreted so, as has been observed in petechial fever by Dr. Graves and Dr. Golding Bird, and in insanity by Dr. Sutherland, and may also occur in diseases of the nervous centres; or it may be caused by a decomposition taking place in the bladder, as in chronic inflammation, or in the case of retention of urine from any cause. In the former case the acid may act as a corrective to the fluids before secretion; in the latter case, after it. But it is not always easy to cause acidity of the urine by any medicines. Mineral acids may be excreted in other ways, and vegetable acids are liable to decomposition in the system. (_Vide_ page 125.)

The use of mineral acids in assisting a weak digestion admits of a simple explanation. For whatever notion we adopt as to the composition of the gastric juice, it is certain that it contains an acid in excess. Now an acid medicine would set free in the blood more of this acid which it is the business of the stomach to furnish, and thus prove useful in that kind of dyspepsia which depends on a failure of the gastric secretion. Hydrochloric acid has been particularly recommended by those who consider it to be the acid normally secreted by the stomach.

When not wanted in the system, it seems probable that acids pass in all cases out of the blood in the same condition as they entered it. Thus vegetable acids act as diuretics; and mineral, as astringents to the glands generally. The latter, when given in excess, may prove hurtful by causing a lithic deposit in the urine. The addition of a mineral acid to healthy urine causes after some time a deposit of uric acid.

The action of acids on the urine is neither so constant nor so certain as that of alkalies. In attempting to correct abnormal conditions of that secretion, it must be remembered that its reaction is liable to great variations in health. The whole amount passed during a day should be examined together. Dr. Bence Jones states that the urine is most alkaline just after meals, and most acid when a sufficient time has elapsed for the completion of the digestive process. (_Animal Chemistry_, p. 51.)

I shall have afterwards to consider the action of the mineral acids as Astringents; and I must now add a few words on that use of the vegetable acids which has gained for them the title of Refrigerants.

In febrile cases of all kinds it is often found that diluent drinks containing the free vegetable acids, or solutions of their salts with alkalies, act beneficially in lowering the pulse, and in moderating the progress of the disorder. These should both be distinguished from mineral saline drinks; for mineral salts, from their known effects on the blood, would seem to belong simply to my division of Catalytics. But the effect of these vegetable acids seems to be to restore the blood to a more natural condition, and this independently of the action of the diluent with which they are administered. Now of this effect there is no certain explanation, but a theory, which may or may not be true, may be ventured to account for it. Should it prove correct, it would seem that in such cases the free vegetable acid acts as a Restorative; and that the alkaline salt of this acid has at first the same action, but adds to it afterwards a Catalytic operation. Let us then attempt to clear up this matter.

It has long been considered probable, but may now be said to have been proved by the researches of M. Becquerel, that in febrile disorders and inflammations there is excreted in the urine an excess of Urea and of Urate of Ammonia, substances which are formed by the oxidation of the Nitrogenous tissues. This extra-oxidation probably arises from a deficiency of that matter which is the proper food of oxygen in the system. This, as we have seen, being the step between grape-sugar and Carbonic acid, must either be Lactic acid, or something similar to it. It must be remembered that no food is usually taken in fever; this would at length quite cut off the usual source of this lactic acid, which is the starch and sugar of the food, and render it necessary that the animal tissues should continue to undergo oxidation, to maintain the animal heat. Now if we compare the commonly received formula of Proteine with those of Lactic acid and Tartaric acid, it will at once be seen, as was pointed out some time ago by Dr. Murray, that the latter contain more Oxygen, in proportion to their Carbon and Hydrogen, than is found in Proteine, or Albumen.

Proteine = C_{40}H_{31}N_{5}O_{12}. Lactic acid = C_{6}H_{6}O_{6}. Tartaric acid = C_{8}H_{4}O_{10} + 2 HO.

Thus, while for 40 equivalents of Carbon, Proteine contains only 12 of Oxygen; Lactic acid contains 40, and Tartaric 50, of that element. So it seems that Albuminous matters, containing less Oxygen, would require much more Oxygen for their combustion; this would produce more heat, augment the number of respirations, and keep up the fever. And though it has been proved by Wöhler that free vegetable acids pass out in the urine without having undergone oxidation, yet the condition of fever would probably be an exceptional case. Lactic acid, the natural fuel, being deficient, the alkali with which it should combine must be present in some excess; so it seems likely that a free vegetable acid would combine at once with this alkali as the Lactic acid would have done, and thus be burnt or oxidized instead of the latter. Its action would then be simply Restorative. Requiring less Oxygen than the Proteine would need to transform it into Carbonic acid, it would thus diminish the number of the respirations, the frequency of the pulse, the temperature of the body,--and in this way allay the fever. It would be strongly confirmatory of this idea if it were proved that the amount of Urea and Urates in the urine is actually diminished by the use of acid drinks and fruits in febrile cases. This hypothesis can only be admitted on the supposition that fever constitutes an exception to the general rule that the vegetable acids pass through the blood without undergoing change.

Now, the salts of these acids, with alkalies, which are often administered in the form of effervescing draughts, might exert the same refrigerant action. But there would be this difference: the alkali of the blood would not be required, the acid being already combined with an alkali. M. Wöhler has found that these vegetable-acid salts always undergo oxidation in the system, being converted into carbonates or bicarbonates, and thus reacting on the secretions as alkalies. And so in the same way it seems that the natural lactate of soda is formed into a carbonate, the carbonic acid being afterwards freed from the base, to be excreted by the lungs. But by this natural process the quantity of alkali in the blood would not be increased, nor would it be augmented by the action of a free vegetable acid. But the change undergone by a salt of this acid would continually add to the alkaline matter already in the system. Now, alkalies have a Catalytic action on the blood, which may prove useful in some sthenic fevers; and therefore these salts have a double action, and are not simply Restorative. (_Vide Alkalies_; _Antiphlogistics_; _Antiscorbutics_.)

Rheumatism and Gout differ considerably from other fevers, both in their nature, and in the remedies which they require. They are produced by special morbid poisons or agencies, which we are enabled to counteract by certain Catalytic medicines. There is in both of them an excess of free acid formed in the system. Remedies which are apparently opposed in nature have proved useful in these complaints. On the Restorative plan, alkalies are the remedies required; for they neutralize the acid. But in spite of this excess of acid, some of the free vegetable acids have been used with advantage, particularly in rheumatic cases. We shall have hereafter to consider how far this operation resembles the common refrigerant action of these remedies just now considered. (_Vide Antiarthritics._) Some obscurity rests upon the subject of the use of Citric acid in scurvy; but as it seems to partake rather of the nature of a Catalytic than of a Restorative action, I have placed Antiscorbutics in the second division.

Now, though there are possibly some exceptions, yet in most cases Acids act as simple Restoratives; but Alkalies certainly operate as Catalytics in some disorders, and have thus to be included in both divisions of Hæmatic medicines.

ORD. III. ALKALIES.

(Potash, Soda, Ammonia, Lime, Magnesia;--their Carbonates, and neutral Acetates, Citrates, and Tartrates.)

We have to consider the alkalies now as Restoratives--treating of those cases only in which they are used to restore a wanting material to the blood or fluids of the body.

That they pass into the blood, is proved by their solubility, and their appearance in the secretions; and that they are natural to it we know, because they are all found in it.

Wöhler has demonstrated the curious fact that the neutral salts of the alkalies with vegetable acids undergo oxidation in the blood, being transformed into carbonates. (I have just said that it seems likely that certain conditions of the system may determine this oxidation, even in the case of the free acids.) Thus it may be easily shown how the neutral (bibasic) tartrate of potash may, with the addition of ten atoms of oxygen, produce two equivalents of bicarbonate of potash, together with four of carbonic acid and four of water.

2 KO, C_{8}H_{4}O_{10} + 10 O=2 KO + 8 CO_{2} + 4 HO. ____________ =2(KO, 2 CO_{2}) + (4 CO_{2} + 4 HO.)

Again, one equivalent of the neutral acetate of potash, with eight of Oxygen, will make one equivalent of the bicarbonate, two of free carbonic acid, and three of water.

KO, C_{4}H_{3}O_{3} + 8 O=KO + 4 CO_{2} + 3 HO. ____________ =KO, 2 CO_{2} + (2 CO_{2} + 3 HO.)

This carbonate, easily decomposed by any acid, is equivalent to a free alkali. Thus these salts fulfil a double function. They may supply the respiratory process, as has already been explained. They also act on the blood, and on the secretions, as alkalies.

Alkalies are used wherever there is an excess of acid in the system, whatever that acid may be. Alkali should naturally be present to neutralize it, for it is unnatural to have a large excess of acid in the secretions, or any excess in the blood. We thus administer alkalies on the restorative principle. They are not always excreted; but whether excreted or not, they tend to render the secretions neutral and alkaline by increasing the quantity of basic matter in the system. Alkalies being more stable than acids, and being more invariably secreted by the kidneys, it is more easy to render the urine alkaline than to make it acid. Alkalies are thus of use in a tendency to lithic acid deposit. The bicarbonates are probably the best for this purpose, for they may be given in large doses, being less irritating. The celebrated Vichy water contains bicarbonate of soda. Lime-water has been used as a solvent for stone. These all act by first diminishing the acid of the blood, and subsequently influencing the secretion of the urine, which secretion, acting as a counterpoise to the condition of the blood, may be generally taken as an index to it.

Dr. Pereira recommends alkalies in cases of dyspepsia and pyrosis, when there is an excess of acid secreted by the stomach. He further thinks it likely that they may aid in the digestion of fatty substances when there is a deficiency of bile. This is quite hypothetical, and depends upon a theory which has been shaken by M. Bernard. The same eminent authority states that Ammonia invariably enters the blood as a salt, and thus can exert no peculiar action beyond the coats of the stomach. I shall state my reasons for doubting this when I consider Ammonia separately in