Part 2
The medicinal uses to which Magnesia has hitherto been applied are in general so well known, that it will be necessary only to give a short summary of the cases in which it is beneficial, for the information of young practitioners, and of those of my readers who may not be acquainted with medical subjects, this medicine being frequently administered without the advice of a physician. If it should appear in the subsequent part of this treatise that Magnesia is possessed of any properties hitherto unsuspected in it, the sagacious reader will in a great measure be left to draw his own practical inferences therefrom.
MAGNESIA ALBA is a powerful absorbent, and is given with great success in disorders of the stomach and bowels arising from acidity. This preparation had been introduced into the materia medica abroad several years before it attracted the attention of our countrymen. The celebrated Hoffman having strongly recommended it to the medical world, some English practitioners began to prescribe it, and Dr. Cadogan bestowing high encomiums on it, in his treatise on the nursing and management of children, it soon made its way into general practice, and supplied the place of the testaceous powders and chalk, which before this period were the medicines usually given to correct acidities in the primæ viæ. The acquisition of this medicine was of the more importance, on account of its entire and easy solution in acids, and of the purgative quality which it possesses; whereas the common absorbents are apt to form concretions, and to induce costiveness; strong objections to their free exhibition, as these properties render them peculiarly unfit for the bowels of tender infants who are particularly liable to diseases of this class.
This tendency to acidity generally attends children during the first months and the time of dentition, and discovers itself when too redundant by the green stools, sour vomitings, gripes and purgings which it occasions: and as the nerves of children are extremely irritable, spasmodic affections are often the consequence of this acrid stimulus being retained in their bowels. In these cases Magnesia may be administered in doses from five to twenty or thirty grains, according to the age of the infant; and in proportion as it is intended to act, either as an alterative, or as an easy purgative.
It has been a common practice to give Magnesia to children as a preventive, and to mix it for this purpose with their food, in order to correct that disposition which milk and the farinaceous aliments have to turn sour. This however should be done with caution, for it is only the excess of acidity which is prejudicial to infants,[l] some degree of it is necessary; and should we too officiously and entirely destroy, what we ought only to restrain within due bounds, we may create disorders of an opposite nature to those we have endeavoured to prevent, and instead of an acid, produce an alkalescent disposition in the first passages. Indeed I fear that diseases have been more frequently created than obviated by the use of preventive medicines, and they should only be allowed in cases where the approach to disease is manifest. But when a child is in a healthy state, the best means to preserve him from a superabundant acidity, is to pay due attention to the regulation of his diet, to give him proper exercise, not to confine him too much in the foul air of hot unventilated rooms, to wash his whole body every day in cold water, and to rub him very well night and morning with a dry flannel, taking care that his stomach be not too full at the time when this friction is performed.
[l] Hactenus monstravimus, sicut cordis, musculorumque vires debiles erant, ita et solidorum quoque statum necessario imbecillem fuisse, et succos tenues, dilutosque; ut natura ampliationem vasculorum facilius efficeret, et incrementum animale minori cum molestiâ perageret. Sed ne status iste tonusque partium debilis laxusque ultra modum procederet (quod sæpe accidit, morbosque excitare solet) acidum quoddam juvenilium animalium stomachis datum est, quod quamvis aluminis instar, lac coagulat, atque ob eam causam aliquando morbum procreat, tamen fibrarum tonum astringet confirmatque, et putredinem omnem alkalinam, a qua alioquin periculum esset, reprimit. Quod quidem videri est, vel in coagulo stomachi vitulini, vel in aliis animalibus: sed istud tamen acidum, quod infantibus tarn idoneum est, redundat fortasse nonnumquam, et vel per testaceas pulveres, vel per medicamenta antiacida, ut supra dixi, corrigi debet.
Russelli OEconomia Naturæ, p. 56.
Nor would I advise parents to rely with too much security on the virtues of this medicine, where the disorders of their children are complicated, or obstinate. The advice of the sagacious and distinguishing practitioner will then be necessary to direct what method of treatment is to be pursued. Nor can I here avoid lamenting that the management of children when diseased, is so often in the hands of nurses and ignorant women, from an absurd notion that their diseases are not proper subjects of medical investigation; when in truth, there are none which require a clearer judgement, a quicker penetration, or a greater share of medical knowledge in the prescriber.
During the period between dentition and puberty, the diseases attendant on a lax fibre still continue, though not so predominantly as in the former stage; yet acescency is the manifest cause, or at least the concomitant of many of the complaints to which children are at this time liable. To this they are disposed, notwithstanding the change in their diet to a more alkalescent kind, by the great quantities of fruit, frequently crude and unripe, cakes, and other sweet and greasy food with which they are too often indulged. By these errors their bowels are overcharged, their digestion impaired, and the aliment remaining too long in the stomach becomes sour, and occasions vomitings, head achs, and other complaints which are often thought to proceed from worms, and indeed are frequently attended with that disorder; as the crudities thus generated in the bowels serve as a nidus for these destructive vermin. Here likewise Magnesia may be of considerable advantage as an alkaline purgative, neutralizing the offending acid, and at the same time promoting its discharge by stool. But if the stomach be overloaded with mucus or undigested aliment, a gentle vomit ought to precede the exhibition of the Magnesia.
And even in a more advanced stage of life, persons of weak habits, and who lead sedentary lives, are often afflicted with indigestion, sour eructations, heart-burn, vomitings, and costiveness. These disorders very frequently attend women during their state of pregnancy, and are sometimes almost instantly removed by the use of Magnesia. Dr. Watson[m] has published the case of a pregnant woman, who was afflicted with such severe vomitings as to bring on convulsions, hiccoughing, and violent pain at her stomach. What she brought up was acid, and so very acrimonious, as to inflame and excoriate her mouth and throat; and the great uneasiness she felt at her stomach upon swallowing any liquor that had the least degree of acrimony, or was more than lukewarm, made it probable that the internal surface of the stomach was affected in the same manner. In this desperate situation, after a variety of remedies had been tried in vain, the stomach was washed with unsalted mutton broth, till the liquor was discharged without any acid taste. Her pain was by this means abated, but in about two hours was apparently returning with the same violence as before. This ingenious Physician then directed a drachm of Magnesia to be given in mutton broth, and to be repeated as often as her pain returned, without any regard to the quantity the whole might amount to, supposing her pain to continue severe. The first dose relieved her, and in three days she took three ounces of Magnesia; and in the next three days, two ounces more, by which time all her symptoms were removed. It is remarkable in this case that a hypercatharsis was not the consequence of taking so large a quantity of Magnesia, where there was so much acid to neutralize it.
[m] Medical Observations and Inquiries, Vol. III. p. 335.
In bilious habits, where there is generally a disposition in the stomach contrary to acidity, Magnesia is usually esteemed to be improper, taken alone: but I am dubious whether this opinion is well founded, and many reasons for these doubts may be deduced from the experiments hereafter to be recited. However, where putrid bile is to be corrected and discharged, by stool, very good purposes may, perhaps, be answered by taking the Magnesia, joined with a sufficient quantity of acid to neutralize it, while in a state of effervescence; or by swallowing the Magnesia and the acid, one immediately after the other, so as to produce the fermentation in the stomach: for thus the fixed air with which the Magnesia so greatly abounds, being let loose, may powerfully correct the tendency to putridity in the contents of the primæ viæ, and at the same time evacuate them downwards.
How far Magnesia may be of service in diseases of the skin I do not take upon me to determine. Several authors have attributed cutaneous eruptions, and indeed the ancient chemists ascribed almost all disorders, to the presence of an acid in the blood; whilst others absolutely deny that an acid can be admitted into the lacteals, or, if admitted, exist in the blood in a state of acidity. In these cases however, if an acid acrimony abounds in the stomach and bowels, with a costive habit, and pale complexion, Magnesia will be a useful corrector, and entering into the circulation in the form of a mild neutral salt, may act as an excellent alterative,[n] proving both diaphoretic and diuretic.
Having thus given a cursory detail of the medicinal properties of Magnesia, in its natural state, I shall now proceed to consider it in a state of calcination: but before any description of its uses in medicine be given, it may be proper to take a view of the changes which are produced in the nature of it by this operation.
[n] Neque enim tantum absorbentem et catharticam, si acidum primâ in regione stabulatur, virtutem exserit; verum etiam si in remissiore dosi, ad grana xv. vel xx. usurpatur, diaphoreticum et diureticum effectum sequi, non semel observavimus.
Hoffman. circa Magnesiam. Oper. Tom. 4. p. 481.
CHAP. IV.
ON THE CALCINATION OF MAGNESIA ALBA.
The free spirit of inquiry, and taste for experimental researches which have of late so happily prevailed, have given rise to several very important discoveries in the course of the last half century; among which, those of the properties of the electrical fluid, and of fixed air, hold a principal rank. That excellent philosopher and experimentalist, the late Doctor Hales, first proved that most bodies contain, as one of their component principles, a quantity of air, differing from that of the common atmosphere in several of its properties. The proportion of this element varies in different substances, and in some constitutes nearly one half of their weight. All calcareous earths, the testaceous powders, Magnesia and alkaline salts contain it abundantly, and have the strongest affinity with it of any bodies, except metals. From all these it is discharged by an acid, and the stronger the acid is, the more sudden and plentiful is the discharge of this vapour, which is of the same nature as that emitted by fermenting liquors. Though it may be inspired in small quantities with impunity, and, as appears from some late observations, even with advantage in some cases,[o] yet it is a known fact that animals expire sooner in a receiver filled with fixed air, than in vacuo. Lastly, it is said to have the remarkable property of rendering putrid substances sweet.
[o] The reader is referred for further information on this subject, to an excellent Treatise on the Management of Pregnant and Lying-in Women, lately published by my worthy and ingenious friend Mr. White; to a volume of Experiments and Observations, by Dr. Percival, which is now in the press; and to some very curious papers on factitious air, which have lately been communicated to the Royal Society, by Dr. Priestley.
In the precipitation of Magnesia, the acid of the Epsom salt uniting with the alkali which is added to the solution, expels the fixed air which the latter contains; but the vapour instead of being dissipated as in the common effervescing mixtures of acids and alkalis, is quietly and immediately absorbed by the Magnesia earth, to which it has a strong affinity; and thus a double elective attraction takes place.
The very large proportion of this element contained in Magnesia Alba has given Dr. Black an opportunity of throwing much light on this hitherto obscure subject; and that excellent chemist has drawn such inferences from the result of his experiments on Magnesia, Quick-lime, and other alkaline substances, as are of the utmost importance to chemistry. As this treatise may fall into the hands of several who may not have an opportunity of perusing the valuable Essays in which these experiments are contained, I shall take the liberty to make a short extract from them, in order to elucidate the subject of the subsequent pages.
The first object of Dr. Black's enquiry was, whether Magnesia could be reduced to Quick-lime. To this purpose, he calcined an ounce of Magnesia in a strong fire. When taken out of the crucible and weighed, it had lost seven twelfths of its weight. Combined with different acids, it formed salts of a similar nature to those constituted by the same acids with the uncalcined powder; but dissolved in them without the least degree of effervescence.
It slowly precipitated the corrosive sublimate of mercury, in the form of a black powder; whereas before calcination a dark red precipitate was formed from the same substance. Mixed with a warm solution of salt ammoniac, it separated the volatile alkali from the acid; but it made no separation of an acid from a calcareous earth, nor did it induce any change upon lime-water; whereas in an uncalcined state, it rendered quick-lime mild. Lastly, being digested for some hours with water, it produced not the least alteration in the water.[p]
[p] In making this experiment some time since, I imagined that Doctor Black had been mistaken in this point, and that some impurity in the water had prevented the success of his process, for I found the water impregnated, as I supposed, with the Magnesia. Flushed with my supposed success, I proceeded to make experiments on the lithontriptic powers of this water, which I found to be very considerable, acting more efficaciously on the human calculus, than either oyster-shell lime water, or a dilute solution of soap ley. I communicated this interesting intelligence to some of my medical friends; but on repeating my experiment several times with different parcels of Magnesia, that the truth of the fact might be absolutely ascertained, I at last was convinced, to my no small mortification, that what I had too sanguinely flattered myself to be a discovery likely to be highly serviceable to mankind, was founded on error; and that the properties communicated to the water proceeded from some calcareous matter which the Magnesia had received by being washed with impure water. I mention this as a caution to every young experimentalist, to be extremely careful in drawing conclusions. However, as something may be learned, even from an unsuccessful experiment, it proves that a very small quantity of lime is sufficient to impregnate a large quantity of water; for I used the calcined Magnesia, in the same proportion as lime is directed for making lime-water, so that very little of it could be quick-lime. And as oyster-shell lime water is a superiour solvent of the calculus to the water prepared with stone lime, is there not some reason to think that the calcareous earth, which has been dissolved in hard water, may, when calcined, be a more powerful lithontriptic, than either of the others? If any inference can be drawn from it, which may in the least promote the interests of mankind, I shall be sufficiently recompensed for the humiliating circumstance of recounting an erroneous experiment.
In pursuing his inquiries, he found that a very small portion of what had been lost in the calcination was water, and that the other part was fixed air, by the loss of which the Magnesia was deprived of its power of effervescing with acids. And from hence the Doctor concluded, that the change made in calcareous substances and in Magnesia by calcination, was chiefly produced by depriving them of this air; and that this volatile Proteus may be conveyed from one body containing it to another body with which it has a greater affinity.
Thus lime being deprived of its air by calcination, and having a stronger affinity with it than alkaline salts have, being mixed with a lixivium of these salts, absorbs all the air from them, deprives them of their property of effervescing with acids, and renders them more acrid, at the same time that the lime becomes mild, and incapable of impregnating water, but recovers its power of fermenting when mixed with an acid.
CHAP. V.
ON THE MEDICINAL VIRTUES OF CALCINED MAGNESIA.
Frequent objections have been made to the use of Magnesia Alba, on account of the great quantity of air which enters into its composition. Whenever it meets with an acid in the stomach they immediately unite; but in forming this union, all the air contained in the Magnesia is discharged with a great degree of effervescence, and recovering its elasticity sometimes occasions very uneasy sensations in weak bowels,[q] inflating and distending them overmuch, inducing griping pains, and above all a sense of debility or sinking, which is not easily described.
[q] Neque tamen præterire possumus, id incommodi nos quandoque ab hoc Magnesiæ pulvere deprehendisse, quod flatulentias et morsicationes in imo ventri reliquerit, si videlicet frequentius in usum trahatur, primaque regio progignendis corrosivis succis, ut in hypochondriacis fieri solet, exposita sit.
Hoffman. Oper. Tom. 4. p. 381.
My much respected friend Doctor Percival, who had often complained of these disagreeable effects from the use of Magnesia, suggested to me the idea of depriving it of its fixed air by calcination, having been informed that they would be obviated by this method. Doctor Black had indeed proved the practicability of the process, but he does not appear to have made trial of the calcined Magnesia as a medicine. In consequence of the above hint I calcined some Magnesia, and was afterwards insensibly led to make further experiments, the event of which, I hope, will be deemed of sufficient importance to apologize for my communicating them to the public.
EXPERIMENT I.
Eight ounces of pure Magnesia Alba were calcined with a strong fire in an air furnace. Three hours calcination were necessary to discharge the whole of the air from the Magnesia. When removed from the fire, it had lost four ounces and three drachms of its original weight, and produced no effervescence with acids; it had not acquired any degree of acrimony to the taste, and when thirty grains of it were diluted with a few spoonfuls of water and swallowed, it occasioned no uneasy sensation in my stomach, nor sense of heat in my throat; proved nearly as aperient as a double quantity of uncalcined Magnesia, and operated without the least griping. It was remarkable that calcination had not reduced the powder in bulk, in proportion to the diminution of its weight.
By the process of this experiment, Magnesia Alba is not only divested of the disagreeable qualities which have been alluded to, but acquires new properties which render it likely to answer some very important practical purposes.
Doctor Macbride, who has with the greatest ingenuity and accuracy, prosecuted the investigation of the nature of fixed air, discovered, that a large quantity of it is discharged in the fermentation of alimentary mixtures; and that the saliva being, in a healthy state, void of air, acts as an absorbent of it, thereby moderating and restraining the discharge of this vapour in the stomach. But when the tone of that viscus is too relaxed to perform the digestion of the aliment with proper vigour, or the saliva is diseased and corrupted, the air expelled from the food becomes too elastic, and produces those disorders which are commonly termed flatulent; and, perhaps, by its effects on that prodigious plexus of nerves which is diffused over the coats of the stomach, may sometimes occasion spasmodic or paralytic affections.
It has been observed above, that calcareous earths, alkaline salts, and Magnesia, being deprived of their air, attract it from every substance with which it has a smaller degree of affinity. The two former becoming highly caustic by the loss of their air cannot be administered but in very small doses. But the calcined Magnesia being absolutely divested of air, though not rendered acrimonious, and being able to absorb a large quantity of this elastic flatus, may act more powerfully than the whole tribe of carminatives, yet essentially differs from them in many respects. _They_ contain a large quantity of air; _Magnesia_ in this state is entirely free from it; _Aromatics_ may be apt to ferment, and increase acidities; the _calcined Magnesia_ is incapable of effervescence, and powerfully corrects an acescent disposition in the gastric juices; the _former_ constipate the belly; the _latter_ is laxative.
From this property of Magnesia, when calcined, of absorbing air, it occurred to me, that it would of all others be the most proper cathartic for patients labouring under the stone, who might be taking the lixivium saponarium, having the advantage over all the vegetable purgatives, which abound with air, and consequently have a tendency to render the caustic alkali mild and inert. I even flattered myself that it might coincide in promoting the efficacy of that powerful solvent of the human calculus. Dr. Macbride's theory, that the lixivium acts by depriving the calculus of its fixed air, appears to be well founded; and Mr. Chittick in the exhibition of his nostrum, which, notwithstanding all his empirical arts to disguise it, is now known to have been the soap ley, kept his patients from every kind of diet abounding with air. We may therefore venture to recommend it, though not as a lithontriptic, being insoluble in water, yet as an assistant to the lixivium, by absorbing a part of that air in the primæ viæ which would otherwise be attracted by the caustic alkali, and thereby render it incapable of acting on the calculus.
In all the diseases attended with an acescent disposition in the first passages, in which Magnesia has been recommended in the third chapter, the calcined powder may be given with superiour advantages, as it will not produce any of those inconveniences, which have been attributed to that medicine when uncalcined. Besides that it will act in a three-fold capacity, viz. as an absorbent of air, and of acidity, and also as an easy purgative. I know several persons who could never bear to take the common Magnesia, with whom the calcined perfectly agrees. It seems likely to be very serviceable in flatulent cholics, and I have been informed of one very obstinate chronical case of that kind, which was greatly relieved, though not perfectly cured by the use of it in the Chester Infirmary, under the direction of a very judicious and ingenious physician.