PHARMACOLOGIA. ON THE OPERATIONS OF MEDICINAL BODIES, AND ON THE CLASSIFICATIONS FOUNDED ON THEM. (continued 2)

105 III. Of Medicines which operate mechanically.

a. By imparting vigour to the respiratory muscles, engaged in the act of expectorating.

It must be admitted that, to a certain extent, expectoration is a voluntary operation, connected with the action of a variety of muscles, which in a state of extreme debility are not easily excited into action: every practitioner must have noticed this fact during the treatment of the coughs of exhausted patients, and have witnessed the distress necessarily arising from it; in this condition, the exhibition of a stimulant may so far renew the exhausted excitability of these organs, as to enable them to undergo the necessary exertions.

b. By compressing the thoracic viscera, through the operation of an emetic.

The beneficial results which frequently attend the concussion of an emetic, in cases of mucous accumulations in the lungs, are too well known and understood to require much elucidation: in the act of vomiting the thoracic viscera are violently compressed, the neighbouring muscles are also called into strong action, and both expiration and inspiration are thus rendered more forcible, and the expulsion of mucus from the cavity of the lungs necessarily accomplished.

The safety and expediency of such a resource must, however, in each particular case be left to the discretion of the medical practitioner.

Besides the remedies above enumerated, there are some others which afford relief in certain coughs, and have therefore in popular medicine, been considered as Expectorants; but their operation, if they exert any, is to be explained upon principles altogether different from that of facilitating expectoration, and will more properly fall under the head of Demulcents.

Atmospheric changes, in relation to moisture and dryness, deserve some notice before we conclude the history of expectorant agents: the subject teems with curious and important facts, and the advantages which the asthmatic patient derives from such changes merit farther investigation. That the lungs are constantly giving off aqueous vapour is made evident by condensing the expired air on a cold surface of glass or metal; and it is easy to imagine that when the atmosphere is saturated with moisture, its power of conducting off this vapour will be proportionably diminished, and that an accumulation of fluid may thus take place in the lungs; on the other hand, we may suppose the air to be so dry as to have an increased capacity for moisture, and to carry off the expired vapour with preternatural avidity; in either of these cases, the excretions from the lungs will be materially influenced, whether to the benefit or disadvantage of the patient will depend, in each particular instance, upon the nature of the disease under which he suffers. I have known a person who could breathe with more freedom in the thick fogs of the metropolis than in the pure air of a mountainous region, and it would not be difficult to adduce many examples in illustration of a diametrically opposite constitution of the pulmonary organs.

From the same cause we may frequently observe remarkable changes 106occur in the character of a cough, at the breaking up of a frost; in some cases the expectoration will be checked, and in others promoted by a sudden change from a dry to a moist atmosphere. Can a more instructive illustration be offered of that important fact, which I have been labouring in every page to impress upon the mind of the young practitioner, that, remedies are only relative agents?

In the course of considerable experience in the treatment of pulmonary complaints, and in the influence of climate and seasons upon them, I have repeatedly observed the rapid transition from moisture to dryness to occasion very remarkable effects upon the disease; and I much question whether an attention to such a condition of the atmosphere does not deserve as much consideration in the election of a suitable place of residence for such invalids, as the more obvious circumstance of temperature. I have been long in the habit of recommending to persons confined in artificially warmed apartments, to evaporate a certain portion of water, whenever the external air has become excessively dry by the prevalence of the north-east winds, which so frequently infest this island during the months of Spring; and the most marked advantage has attended the practice. But in such cases the practitioner must ever be guided by the symptoms of each particular case; it would be worse than useless to lay down any general precept for his guidance. We cannot then be surprised that such a difference of opinion should exist amongst practitioners of equal eminence, respecting the influence of a marine atmosphere; some advocating its advantages to the pulmonary invalid, and others maintaining with equal confidence the injurious tendency of such localities; each party appeals to experience in justification of his opinion, and with equal candour and justice; but the cases from the results of which the medical inference has been drawn, however parallel they may have appeared, differed in those essential points to which we have alluded, and upon which the question of climate would seem to turn. There is another circumstance connected with the subject of atmospheric moisture which it is also essential to remember,—that the air gains a considerable increase in its power of conducting caloric, by becoming saturated with aqueous vapour; thus, when a thaw takes place, and the thermometer rises a few degrees above 32°, the air, instead of impressing us with the sensation of increased temperature, actually appears much colder.

SIALOGOGUES;

Substances which increase the salivary^[166] discharge. This class comprehends two orders of medicines, viz.

1st. Those which increase the salivary excretion by external application to the secreting vessels, by mastication, as the following acrimonious and pungent substances, Anthemis Pyrethrum; Colchearia Armoracia; Daphne Mezereum; Nicotiana Tabacum, &c.

2nd. Those whose internal exhibition affects these organs through the medium of the circulation, of which Mercury is the only true example; for all the preparations of this metal, when administered in certain quantities, produce salivation.

The acrid Sialogogues, or Masticatories, by stimulating the excretory 107ducts, and increasing the secretion of saliva, sometimes relieve the pain of tooth-ache, and are commonly resorted to for that purpose; they are besides supposed capable of relieving other congestions, or inflammatory dispositions, in remote parts of the head, by the derivation they occasion from the neighbouring vessels, especially the branches of the external carotid.

Mercury, in its metallic state,^[167] is perfectly inert, and does not exert any influence whatever upon the living body: this fact is sufficient, if any serious refutation were necessary, to overturn the theory which attributes its sialogogue property to the gravity of its particles, by which “it is disposed to retain the direct line in which it is propelled from the heart, and is therefore more certainly determined to the vessels of the head.” It has been also supposed to act by diminishing the lentor of the blood, and disposing it to pass more easily into the salivary glands, so as to increase their secretion: equally gratuitous and improbable are the chemical hypothesis which have been offered to explain this curious and singular property; Dr. Cullen endeavoured to solve the problem, by supposing that “Mercury has a particular disposition to unite with ammoniacal salts, and that such salts are disposed to pass off by the salivary glands more copiously than by any other excretion.” Dr. Murray, however, very justly remarks that mercury has not any peculiar tendency of this kind; and that if it had, these salts are not more abundant in the saliva, than in some other secretions. Dr. Murray then proceeds to submit a theory which he considers better calculated to explain the phenomenon; he observes, that the urine appears more peculiarly designed to convey matter which has been received into the circulating mass, but which is still excrementitious, from the system. To pass, however, with this fluid, it is necessary that the matter conveyed should be soluble in it; and when it is so, we can discover it in the secretion by chemical tests. If there is any property connected with it, therefore, which shall prevent this solubility, it probably will prevent the substance from being secreted. Now, the phosphoric acid, abundant in urine, must in this mode counteract the secretion of mercury in any form of preparation, by forming with it a compound, insoluble, and to which the slight excess of acid cannot communicate solubility; the mercury, therefore, existing in the circulating mass, when brought in the course of the circulation to the secreting vessels of the kidneys, will not pass through their whole course; but if conveyed so far as to be combined with phosphoric acid, will, from this combination, be incapable of being conveyed onwards, and will therefore be retained in the composition of that part of the blood which does not enter into the secretion, but returns into the circulation. It must be discharged by some other emunctory; a portion of it appears, from some facts, to pass off by the insensible perspiration; but the tenuity of this secretion, if the term may be employed, must be unfavourable to this mode of discharge. The salivary secretion is one by which it may be more easily transmitted; and this transmission may even be facilitated by the affinity exerted to the Oxide of Mercury by the Muriatic Acid, the Soda, and Ammonia, which are the chief saline ingredients in saliva; for it deserves to be remarked that triple compounds of these substances are, to a certain extent, soluble in water; and if the Mercury 108is thus secreted, it will of course stimulate the secreting vessels through which it passes, and increase the discharge.

Sir Gilbert Blane^[168] has lately advanced another hypothesis to account for the effects of mercury as a sialogogue; he considers the salivary glands as one of the outlets for the ramenta of the bones, for by analysing the saliva we discover the principles of which they consist; indeed the osseous matter not unfrequently concretes on the teeth, and sometimes on the salivary ducts, in the form of what is called Tartar: “does not this fact,” says Sir Gilbert Blane, “in some measure account for these glands being the parts upon which determination is made by the operation of mercury, which consists in exciting an active absorption of solid parts, as I have elsewhere observed?”^[169]

But do not the kidneys, and other excretory glands also furnish outlets, through which the detritus of the body is eliminated. How does it happen, therefore, that the kidneys are not as equally affected as the salivary glands by the action of mercury? In the present state of our knowledge it will be more prudent to rest on the phenomenon as an ultimate fact, than in attempting to ascend higher in the scale of causes, to involve ourselves in impenetrable darkness.

During the prevalence of the theory which attributed to Nitric acid all the antisyphilitic powers of mercury, it was even maintained that this acid also excited ptyalism; experience however has disproved the effects thus attributed to it, and no one attempts to support its pretensions, as a sialogogue, except indeed as it may perchance, by its acrid qualities, influence the excretory ducts of the glands, externally, in the act of being swallowed.

It has very lately been stated by Dr. Macleod,^[170] that the Hydro-cyanic acid occasionally produces soreness of the gums, and a disposition to ptyalism; this, if true, is a very remarkable fact, and well deserves attentive consideration.

Some theorists may, perhaps, be inclined to consider certain Nauseating Medicines as possessing sialogogue properties. It cannot be denied that an increased discharge of saliva will take place during the operation of such remedies, but it is very transient, and can never be rendered available to any therapeutic object. I shall however have occasion to refer to this fact hereafter, and to the inference deduced from it by Dr. Eberle, in explanation of the effect of nauseating medicines in promoting the operation of Mercury.

ERRHINES, or STERNUTATORIES:

Substances which, by direct application to the pituitary membrane, occasion a discharge from the nostrils either of a mucous or serous fluid. This class contains several different species, whose operation varies in intensity, as well as in duration.

Errhines have been regarded as useful in consequence of the evacuation they occasion, but in this respect their value has been greatly over-rated; it has been stated, that they diminish the quantity of fluid circulating 109in the neighbouring vessels, and even extend their influence to all the branches of the external carotid; and Dr. Cullen says that he has, apparently from this operation, known head-ache, pain of the ear, and some cases of ophthalmia, cured or relieved by the use of Errhines. There can be no doubt that local stimulants of this kind will frequently remove pain from the head and neighbouring parts, but not merely by occasioning vascular depletion, as Dr. Cullen supposed, but by a stimulant operation conveyed through the medium of nervous communication, or contiguous sympathy.

Dr. Cullen has moreover supposed, that these substances may be useful in preventing apoplexy or palsy. Morgagni^[171] however relates a case in which sneezing induced a fatal attack of this disease; and Van Swieten^[172] has satisfactorily shewn, that continued paroxysms of sneezing tend to load the vessels of the head with blood; for the violent contraction of the chest impedes, for a time, the passage of the blood through the lungs, and therefore obstructs the return of the venous blood from the brain, the vessels of which are in consequence greatly distended; the face therefore reddens and becomes turgid, the eyes are suffused with water, and appear full and distended. Its occasional dangerous violence is said to have given origin to the benediction so universally bestowed on those who sneeze.^[173]

It has been a subject of popular inquiry, how far the habitual use of Snuff may prove beneficial or injurious; and whether the habit, when once fully established, can be discontinued with impunity? It may be remarked that Snuff, by habitual use, soon ceases to produce the effect of an Errhine, for which reason its discontinuance cannot, generally, be regarded as likely to be attended with any danger; in those cases, however, in which the discharge is perpetuated, a contrary judgment should be pronounced, for all artificial discharges become constitutional by long continuance, and can therefore be seldom checked with impunity. Dr. Cullen states, from experience, that “whenever the nasal discharge has been considerable, the laying aside the custom of taking snuff has been productive of evil.”

EPISPASTICS. Vesicatories. Blisters.

External applications to the skin, which produce a serous or puriform discharge, by previously exciting a high state of inflammation.

When these agents act so mildly as merely to excite inflammation, without occasioning the effusion of serum, they are denominated Rubefacients.

Various substances have at different times, been proposed for the accomplishment of this object,—such as Nitric Acid, Boiling Water, Strong Acetic Acid, Tartarized Antimony, &c. It is, however, generally admitted, that no substance ever employed equals in efficacy, or certainty, the Cantharis Vesicatoria, the common blistering, or Spanish fly; and whose effects may serve to illustrate the modus operandi of this class of remedies.

110By the application of a Blister, the extreme blood vessels are excited into increased action, by which inflammation is occasioned, and the exhalants made to pour out a thin serous fluid which separates the cuticle from the true skin, and forms a vesicle or blister.

From this simple view of the subject it will appear evident, that blisters may produce their salutary effects by several different modes of operation; by a just estimate of which the practitioner will be enabled to reconcile the discordant opinions which have been delivered upon the subject, and to employ these agents with greater satisfaction and advantage.

Blisters may act—

1. As Derivatives, i. e. by producing a derivation of the circulation from the inflamed and engorged vessels of the neighbouring organs to the blistered surface. This mode of operation was long overlooked by the physicians, who ascribed all the beneficial effects of a blister to the evacuation which it produced, while the humoral pathologist, moreover, considered the matter so discharged to be of a morbific nature. That such agents owe their salutary tendency to causes independent of their powers as evacuants, is at once rendered evident by the relief which they afford, when used only as Rubefacients.

2. As Evacuants—by occasioning an effusion of Fluids. In this case the vesicated part may be considered in the light of a new excretory organ, the formation of which requires the establishment of a new current or determination of blood; so long as the discharge continues, so long will there be an especial demand of blood in the blistered part, and a consequent derivation of the circulation from the inflamed and engorged vessels of the neighbouring organs.^[174] The nature of the fluid effused is at first serous, but after some time it becomes purulent, and this stage of its operation must be considered as, by far, the most beneficial; hence the great advantages derived from a “perpetual blister.”

3. As General Stimulants, by raising the vigour of the circulation.^[175] That Blisters have such a tendency there exist too many proofs to allow us to doubt. Hence in fevers they frequently prove valuable auxiliaries, but since the application of any stimulus, in such diseases, must be regulated by the degree of excitement, it is evident that they can only be made with success in particular stages; this simple fact will at once explain the cause of that want of unanimity in Physicians with respect to the value of blisters in febrile diseases. Rush considered that there was one particular period, in the course of a continued fever, intermediate between its stage of high excitement and the appearance of a collapse, in which blisters will generally produce unequivocal good effects, and to this he gave the name of the Blistering point.

4. As Antispasmodics.—Relieving pain through the medium of Contiguous Sympathy. This effect would frequently appear to be independent of the operations above enumerated; a similar principle seems to exist 111with regard to the pain excited by blisters, which may also be applied to the explanation of the advantages derived from them in several diseases. It has long been remarked that, by exciting one pain we may often relieve another, and hence blisters afford relief in tooth-ache, and other painful affections. Epilepsy and Hysteria, arising from irritation, have been removed by such applications, apparently from their exciting powers.

It remains for us to make a few observations upon the abuse of these remedies, for, notwithstanding the popular adage that “Blisters are always safe things,” that “if they do no good, they can do no harm,” they will be found, like all other potent applications, capable of producing much mischief when directed by unskilful hands. In stages of high vascular excitement in the pulmonary organs, blisters have increased the irritation they were designed to allay, and in some cases have promoted a tendency to effusion; in the treatment of acute Hydrocephalus the common practice of blistering the head appears very questionable, and has too often, I am well persuaded, accelerated the fatal termination, by increasing the disposition to serous effusion.

ISSUES (Fonticuli) and Setons (Setacea^[176]).

The effects of these processes bear a strong analogy to those which are produced by Vesicatories; they are, however, more permanent, and are on that account better adapted to the relief of those chronic affections which would seem to require a remedy of long continued influence. In pulmonary affections, for instance, a seton in the side is frequently attended with very considerable benefit. The popular belief in humoral pathology, which continues to influence the mass of mankind, has perhaps assigned to these remedies a greater share of credit than that to which they are really entitled, but it must still be acknowledged that when an ulcer having existed a great length of time, is healed or dried up, or any constitutional discharge is suddenly checked, the health may become affected. In such cases the establishing a discharge by means of an Issue is undoubtedly a safe, and often a beneficial operation.

III. OF CHEMICAL REMEDIES.

There is no principle in physiology better established than that which considers vitality as a power engaged in continual conflict with the physical, chemical, and mechanical laws, to which every species of inanimate matter is invariably subject. Every phenomenon of the living body might be advanced in illustration and support of this general position. The animal machine is constantly surrounded and assailed by agents, whose elective attractions for the principles of which it consists, are so numerous and energetic, that its decomposition would inevitably and speedily result, were not the adhesion of its molecules maintained by the conservative influence of a superior power. The compositions and decompositions which manifest themselves in the elaborate operations of chylification, 112sanguification, and secretion, are carried on by agencies totally distinct from those which govern the combinations of inert matter, and must be investigated upon principles essentially different. How then, it may be asked, can a medicinal substance be brought to act chemically upon the living body? Notwithstanding the general proposition, that the animal processes to which we have alluded, are governed by laws peculiar to life, yet it must be admitted that such processes are occasionally influenced,^[177] modified, and controlled by powers strictly chemical in their operation; although in some cases it will be seen that such effects afford only apparent exceptions to the general law: for several of the remedies whose operations have been regarded as purely chemical, exert their influence on parts which cannot be strictly considered under the control of the living principle; of which Antacids, and certain Antidotes and Antiseptics, to be hereafter explained, may be considered as examples: in like manner will cataplasms of acetic acid hasten the exfoliation of carious bone; a practice which has lately been employed with much success in the Infirmary at Gloucester. Upon the same principle alkaline applications may be made to dissolve coagulated blood; suppose, for the sake of illustration, that the bladder should become filled with coagulum through hemorrhage from the prostate gland, and that the most serious consequences were to be apprehended from the distention; in such an emergency, a dilute and tepid solution of potass, if injected through the catheter, might prove eminently serviceable; although such a practice would require the utmost skill for its safe direction, since the removal of the plug, thus afforded by Nature to the bleeding vessel, might be followed by an immediate return of active hemorrhage. On the contrary, other agents destroy the vitality of the organ before they can produce any change in the matter of which it is composed, as the action of Escharotics will clearly demonstrate.

113

REFRIGERANTS.

Substances which directly diminish the force of the circulation, and reduce the heat of the body, without occasioning any diminution of sensibility or nervous energy.

These remedies may be considered either as external and local, or as internal and general. In the first case, there will not be much difficulty in substantiating their claims to be considered Chemical Agents, but in the latter case, the theory of their operation is unsatisfactory and obscure; and even the facts which are adduced to establish the existence of such a class of remedies, are of a very problematical character.

Topical Refrigerants. In the case of external inflammation, refrigeration may be produced by the application of cold substances, such as water, ice, or certain saline solutions, or by the abstraction of heat by means of evaporation, which is very effectually accomplished by the use of lotions composed of spirit or ether. By these methods we are capable of directly diminishing the activity of the vessels of the part; thus, in burns and scalds, the pain is instantly relieved, and the inflammation effectually reduced.

Internal Refrigerants. There are certain saline substances which, by undergoing a rapid solution, and acquiring an increased capacity for caloric, produce a diminution of temperature, and if this takes place in the stomach, the sensation of cold which it will produce is equivalent to a partial abstraction of stimulus; which, being extended by sympathy to the heart, occasions a transient reduction in the force of the circulation, and by this, or by a similar sympathetic affection, causes a sensation of cold over the whole body; in this manner Dr. Murray explains the refrigerant operation of nitre, which after all is of a very doubtful nature. We shall perhaps not feel much difficulty in accepting this theory, and in allowing that general refrigerant effects may be temporarily produced, by occasioning an impression of cold upon the stomach. The theory which is proposed to explain the refrigerant operation of vegetable acids and certain other substances, and which we have now to consider, is derived from those chemical views respecting animal heat, in which the consumption of oxygen in the act of respiration is considered the principal source. Dr. Murray,^[178] who has given a luminous exposition of this theory, says “it is established by numerous experiments and observations, that the quantity of oxygen consumed in the lungs is materially influenced by the nature of the ingesta received into the stomach. When the food and drink are composed of substances which contain a small proportion of oxygen, it is known that the consumption of oxygen in the lungs is increased, and this even in a short time after the aliment has been received; thus Mr. Spalding, the celebrated diver, observed, that whenever he used a diet of animal food, or drank spirituous liquors, he consumed in a much shorter time the oxygen of the atmospheric air in his diving-bell; and therefore he had learned from experience to confine himself to a vegetable diet, and to water for drink, when following his profession.”^[179] During digestion 114too, it was established by the experiments of Lavoisier and Seguin, that a larger proportion of oxygen than usual is consumed.

But it is known, that the animal temperature is derived from the consumption of oxygen gas by respiration; and, that an increase in that consumption will occasion a greater evolution of caloric in the system, and consequently an increase of temperature in the body, while a diminution in the consumption of oxygen will have an opposite effect. If, then, when the temperature of the body is morbidly increased, we introduce into the stomach substances containing a large proportion of oxygen, especially in a loose state of combination, we may succeed in reducing the general temperature. This we accomplish in part by a vegetable diet, but still more effectually by the free use of the Acids. The vegetable acids in particular, which are found by experience to be the best refrigerants, are readily acted upon by the digestive powers, and assimilated with the food; and as the large quantity of oxygen which they contain is already in a concrete state, little sensible heat can be produced by the combination of that element with the other principles of the food. The nutritious matter which is received into the blood, containing thus a larger proportion of oxygen than usual, will be disposed to abstract less of it from the air in the lungs, and consequently less caloric will be evolved; the temperature of the body will be reduced; and this, again operating as a reduction of stimulus, will lessen the number and force of the contractions of the heart.

Such is the philosophical web which chemical ingenuity has wove for us,—the device is beautiful, but the fabric will be found too frail to endure the touch. The experiments of Dr. Crawford, in proof of the chemical origin of animal heat, are highly ingenious and plausible, but it is now generally admitted that the temperature of animals depends upon the living principle^[180] which animates them, and that although the absorption of oxygen, in the act of respiration, may directly contribute something to its production, yet that its chief action is that of serving as a stimulus to the living power in generating it; for, as Sir Gilbert Blane^[181] remarks, oxygen plays an interesting and active part as an exciting power throughout all nature, both animate and inanimate. If the heat of the body depended on respiration alone, any one might, by a voluntary effort of quick, deep, and prolonged respiration, increase the temperature of his body at will; the effect also of the emotions of the mind, in generating both heat and cold, adds Sir Gilbert, is proof sufficient of temperature depending on a vital, and not on a chemical cause.

ANTACIDS:

Remedies which obviate acidity in the stomach, by combining with the acid, and neutralizing it.

This is the most decided instance of chemical action which occurs in the history of medicinal operations. We have an acid whose presence excites morbid symptoms in the primæ viæ, and these are immediately removed by the administration of any one of those substances which are capable of forming a natural compound with the acid in question, out of the body, and the same proportions are required in both cases for saturation. 115If a carbonated alkali be employed, the same disengagement of carbonic acid takes place in the stomach as would occur in the laboratory, and a new compound is produced, whose operation varies according to the chemical nature of the substance employed; thus, the salt which magnesia forms with the acid in the stomach proves slightly purgative, while that which lime produces under similar circumstances is distinguished by an opposite property.

ANTILITHICS and LITHONTHRYPTICS.

Antilithics^[182] are remedies which have the power of preventing the formation of those mechanical deposites from the urine, which give origin to calculous concretions; and may belong either to the class of Vital, or Chemical Agents.

Lithonthryptics^[183] are those medicines which, by a chemical operation, are capable of dissolving calculous concretions.

It has been already shewn, while treating the subject of Diuretics, that certain substances, when internally administered, are capable of passing the barriers of digestion, and of entering the circulation; and that, moreover, these bodies may be again separated by the secretory vessels of the kidneys, and be ejected from the body in the urine. It cannot therefore be contended, that the urinary calculus is placed beyond the sphere of direct medicinal influence, nor can any argument, founded upon the alleged incompatibility of chemical and vital action, be fairly maintained in this case; for the urinary calculus, as well as the urine itself,^[184] may very justly be considered as extraneous to the living body. The existence of such a class of remedies as that of Lithonthryptics being thus established, we have to consider the mode and possible extent of their operation in the different varieties of the disease, which they are thus calculated to palliate or cure. In entering upon this inquiry, it is not my intention to prosecute the subject farther than may be necessary to explain the modus operandi of the remedies in question, and in conformity with the object and plan of this work, to establish some general principles that are to direct us in their election, combination, and administration; for farther details the practitioner must consult the systematic treatises of Prout^[185] and Marcet,^[186] and the very able papers of Mr. Brande,^[187] and Dr. Wilson Philip.^[188]

The urine may be considered as one of the most heterogeneous of the animal fluids;^[189] and since a knowledge of its composition, and that of the 116morbid changes of which it is susceptible, must constitute the basis of all our knowledge respecting the formation and cure of calculous affections, the following results of an elaborate analysis by Berzelius, are submitted with a view to elucidate our pathological researches.

Animal Principles. Water 933·00

Urea 30·10

Lithic Acid 1·00

Pure Lactic Acid, Lactate of Ammonia, and Animal matters not separable from these 17·14

Mucus of the Bladder ·32

Alkaline and Earthy Salts. Sulphate of Potass 3·71

Sulphate of Soda 3·16

Phosphate of Soda 2·94

Phosphate of Ammonia 1·65

Muriate of Soda 4·45

Muriate of Ammonia 1·50

Earthy Phosphates with a trace of Fluate of Lime 1·00

Silex ·03

1000·00

Besides the above ingredients, which appear to be essential to healthy urine, Dr. Prout observes that in different diseases it may contain Albumen, Fibrin, and the red particles of the blood; Nitric acid; various acids, which are found to be modifications of the Lithic; Oxalic acid; Benzoic acid; Carbonic acid;^[190] Xanthic Oxide; Cystic Oxide; Sugar; Bile; and Pus.

It will be necessary in this place to make a few observations upon the nature and habitudes of those principles, which are more immediately active in the production of calculi—

1. Urea is a principle peculiar to urine, and must be regarded as a result of the action of the kidneys upon some of the constituents of the blood, perhaps, as Dr. Prout suggests, upon its albuminous matter. For a long time it was regarded as the peculiar principle upon which the colour and other sensible qualities of the urine depended; Berzelius however has corrected this fallacy, and considers that the Lactic acid, and its accompanying animal matters, are the bodies which impart to this fluid the characteristic smell and colour which distinguish it.^[191]

1172. Lithic, or Uric^[192] Acid. As this principle is not found in the blood, but is constantly present in healthy urine, it follows that it must be generated by the action of the kidneys. M. Majendie^[193] has lately endeavoured to prove that its secretion depends upon the Azote received in alimentary substances, and for the following reasons, viz. 1. Azote is a component part of Lithic Acid^[194]—2. Those persons who use a large portion of animal food, and fermented liquors, are liable to calculous disorders—3. When animals are confined to food which contains no Azote, no Lithic acid is formed—but of this anon.—Berzelius and other animal chemists have supposed that this acid exists in urine in a free state; but Dr. Prout, whose arguments appear very satisfactory and decisive, is of opinion that it is always in combination with ammonia (Lithate of Ammonia), from which however it is very easily separated by the addition of any acid, even the carbonic, in the form of a red powder. It moreover appears to be susceptible of several important modifications, with which it behoves the pathologist to be acquainted; the profession is greatly indebted to the ingenuity and industry of Dr. Prout for some very essential additions to our knowledge, respecting the habitudes of Lithic acid with different bodies.

Erythric Acid. When nitric acid diluted with about an equal bulk of water, is poured upon pure lithic acid, and a moderate heat is applied, an effervescence takes place, and the lithic acid is dissolved; if we then concentrate this solution by a gentle evaporation, we obtain transparent colourless crystals, which have been found to constitute a peculiar acid, to which M. Brugnatelli has given the name of Erythric acid.

Purpuric Acid. Dr. Prout has discovered that if into a strong solution of the above crystals in water, whilst boiling hot, we carefully drop some pure ammonia, the solution acquires a beautiful purple^[195] colour, and crystals of purpurate of ammonia speedily begin to form and subside. If these crystals are treated by means 118of potass and sulphuric acid, pure Purpuric acid is obtained in the form of a yellowish, or cream-coloured powder.

3. The Phosphates. As the Phosphoric acid and its compounds perform an important part in the generation of calculi, their origin^[196] and history demand particular attention from the chemist. The Phosphoric acid frequently exists in the urine in a free state, when it would appear to act, like any other acid, as a precipitant of the Lithic acid; this however is not the circumstance that renders its presence formidable; it is to the abundance of its compounds that we are to look for mischief. In healthy urine the phosphoric acid appears to exist in union with soda and ammonia, and partly with lime and magnesia; the latter salts being retained in solution by an excess of acid; but the proportion of these bodies is liable to considerable variation.^[197]

Having thus briefly noticed those particular points in the chemistry of the subject with which the therapeutic principles are more immediately connected, we shall be better prepared to examine and appreciate the several plans of treatment which have been proposed for the prevention, cure, or palliation of calculous disorders; and here the subject naturally divides itself into two parts; the one comprehending the modus operandi of Antilithics, or those remedies which prevent or correct the calculous diathesis; the other, explaining the solvent action of Lithonthryptics over concretions already formed.

The line of demarcation by which healthy and morbid urine are separated, is so slight that it is difficult to define its limits; nor would the circumstance appear to be materially important, for the boundary is daily exceeded, not only with impunity, but even without our consciousness of the event; and Dr. Prout has accordingly denominated such occasional deviations, the “Sediments of Health.”

The same enlightened author considers that mechanical deposites from 119the urine, although composed of the same general ingredients, may, in a pathological point of view, be conveniently divided into three classes, viz. Pulverulent or Amorphous Sediments; 2. Crystalline Sediments, usually denominated gravel; and 3. Solid Concretions, or calculi formed by the aggregation of these latter sediments. The first of these may be passed over, as unconnected with the present subject; the latter however constitutes an essential object of research; for a complete acquaintance with the chemical history of calculi can alone furnish the true indications of cure.

Scheele,^[198] with whom the inquiry originated, conceived that every calculus consisted of a peculiar concrete acid, soluble in alkaline lixivia, and which Morveau denominated the Lithic Acid; but the subsequent researches of Fourcroy, Vauquelin, Wollaston, Pearson, Henry, Brande, Marcet, and Prout, have demonstrated the existence of several bodies in the composition of urinary calculi, viz. Lithic Acid; Phosphate of Lime; Ammoniaco-magnesian Phosphate; Oxalate of Lime; Cystic Oxide;^[199] and Xanthic Oxide;^[200] to which may be added an animal cementing ingredient. The varieties of calculi produced by the combination or intermixture of these ingredients, are represented in the following Tabular Arrangement.

120

A TABULAR VIEW OF THE DIFFERENT SPECIES OF URINARY CALCULI.

Species of Calculi. EXTERNAL CHARACTERS. CHEMICAL COMPOSITION. REMARKS.

1. Lithic or Uric. Form, a flattened oval; Specific gravity, generally exceeds 1·500; Colour, brownish or fawn-like; surface smooth, texture laminated. It consists principally of Lithic Acid; when treated with nitric acid, a beautiful pink substance results. This calculus is slightly soluble in water, abundantly in the pure alkalies. It is the prevailing species; but the surface sometimes occurs finely tuberculated. It frequently constitutes the Nuclei of the other species.

2. Mulberry. Colour, dark-brown; texture, harder than that of the other species; Sp. grav. from 1·428 to 1·976. Surface, studded with tubercles. It is Oxalate of Lime, and is decomposed in the flame of a spirit lamp, swelling out into a white efflorescence, which is Quick-lime. This species includes some varieties which are remarkably smooth and pale coloured, resembling a hemp seed.

3. Bone Earth. Colour, pale brown or gray; surface smooth and polished; structure, regularly laminated; the laminæ easily separating into concrete crusts. Principally Phosphate of Lime. It is soluble in muriatic acid.

4. Triple. Colour, generally brilliant white; surface uneven, studded with shining crystals; less compact than the preceding species; between its laminæ, small cells occur, filled with sparkling particles. It is an Ammoniaco-magnesian phosphate, generally mixed with phosphate of lime; pure alkalies decompose it, extricating its ammonia. This species attains a larger size than any of the others.

5. Fusible. Colour, greyish-white. A compound of the two foregoing species. It is very fusible, melting into a vitreous globule.

6. Cystic. Very like the Triple Calculus, but it is unstratified and more compact, and homogeneous. It consists of Cystic Oxide; under the blow-pipe it yields a peculiarly fetid odour. It is soluble in acids, and in alkalies even if they are fully saturated with carbonic acid. It is a rare species.

7. Alternating. Its section exhibits different concentric laminæ. Compound of several species, alternating with each other.

8. Compound. No characteristic form. The ingredients are separable only by chemical analysis.

121Let us now inquire into the circumstances under which the several substances enumerated in the foregoing table, are found to be deposited; and first of the Lithic acid Diathesis. It has been already stated, that the lithic acid exists in the urine in combination with ammonia, so as to be held in solution under ordinary circumstances; if however any free acid be generated, the lithic acid is immediately precipitated, giving rise to the appearance so well known under the name of red gravel; from this view of the subject the lithic acid deposite must be considered as arising, not from the excess of that substance in the urine, but from a decomposition of the compounds into which it enters by the agency of a free acid. M. Majendie is therefore incorrect in attributing its appearance to the quantity of azote in the ingesta; an opinion which has been very ably controverted by Dr. Philip, in a paper published in the sixth volume of the Medical Transactions. It appears, moreover, that whatever tends to disturb the process of digestion, by favouring the production of acid, may be considered as the exciting cause of the lithic deposites; especially where the cutaneous functions are imperfectly performed; for Dr. Philip is of opinion, that the precipitating acid, in a healthy state of the system, is thrown off by the skin; and he supposes that even when generated in excess, it may be diverted to the surface of the body by merely increasing the insensible perspiration. The medical treatment of the lithic diathesis is thus rendered simple and satisfactory; and if the opinion of Dr. Prout be true, that at least two-thirds of the whole number of calculi originate from lithic acid, the extreme importance of the subject is too apparent to require comment. Remedies, medicinal and dietetic, that are capable of correcting dyspeptic symptoms, such as slight bitters,^[201] will doubtless prove valuable resources; while all those agents which have a tendency to correct and regulate the insensible perspiration, will necessarily fall under the head of anti-lithic remedies. Mr. Copland Hutchison, in a paper which has been published in the Transactions of the Medico-Chirurgical Society, has shewn a comparative rarity of calculous disorders in British seamen. Can the quantity of muriate of soda taken with their food, from its stimulating influence upon the cutaneous functions, be considered as affording a plausible explanation of this fact? The Phosphatic Diathesis seems to be accompanied with considerable derangement of the chylo-poietic viscera, and Dr. Prout very justly remarks, what I have frequently observed, that the stools are extremely unnatural; as the phosphates are retained in solution by an excess of acid, it would appear as if an alkaline principle was occasionally developed, and it is not unreasonable to suppose that this may be sometimes derived from bilious regurgitations;^[202] in some cases, the alkali is derived from the spontaneous decomposition of urine itself, especially where the bladder has lost its governing power,^[203] as 122from some injury^[204] of the spine; or from some local affection of the bladder or prostate gland; wherever the urine undergoes an incipient process of decomposition, ammonia will be generated, and an ammoniaco-magnesian phosphate^[205] be immediately precipitated: hence in cases where the bladder is unable to discharge its contents, this deposite is very apt to take place, as in diseases in the prostate; and this explains the reason why the triple phosphates are so frequently formed in elderly people, who cannot wholly evacuate their bladder.

It will appear evident from these cursory observations, that some varieties of Calculi will be influenced by acids, and others by alkalies, and that the exhibition of such remedies will be liable to palliate, or to aggravate the symptoms, according to the character and composition of the offending calculus, and according to the prevailing diathesis of the patient; as a general rule to direct us in the chemico-medical treatment of these cases, Dr. Marcet states, that “Whenever the lithic acid predominates, the alkalies^[206] are the appropriate remedies, but that when the calcareous or magnesian salts prevail, the acids are to be resorted to.” But if it be asked how we are to discover the nature of the calculous affection, so as to direct the suitable remedy? the reply is obvious—by an examination of the sediment deposited by the recent urine, or by an analysis of the small fragments which are frequently voided with it; the Phosphates subside from the urine as a white, lithic acid, generally, as a red deposit; and since the phosphates are held in solution in the urine by an excess of acid, it is evident that whenever such acidity is diminished by the hand of Nature or art, a white sabulous deposit will ensue; hence, says Mr. Brande, it occurs in the urine of persons who drink soda water, or take magnesia; the remedy of such a deposit, when it takes place habitually, is a course of acidulous medicines; on the contrary, since lithic acid is precipitated by the acids, alkalies are naturally suggested for the prevention of that deposit. In the compound calculi, acids and alkalies may be equally injurious or beneficial, for since these bodies are composed of a variety of ingredients, the action of any one solvent must be partial, and may convert the smooth calculus into a rough and highly irritating body, or vice versa. In the alternating calculi it may be judicious to exhibit these remedies alternately, as the symptoms of the case and the deposit of the urine may indicate. After all, however, the solvent powers of Lithonthryptic remedies must be very limited, and in advanced cases we can never expect to procure more than palliation. With respect to the agency of these different remedies, as Antilithics, I would observe, that while experience bears us out 123in confiding in the production of certain chemical effects from their use, we must not forget that much is to be effected by their judicious administration as vital agents: and it will be hereafter my duty to point out the many advantages that may be obtained, by combining in one formula, medicines which individually belong to each class.

Independent of any chemical effect, alkaline substances are found by daily experience to allay the morbid irritability of the urinary organs in a manner not yet explained; alkalies may also prove generally serviceable in these disorders, by acting immediately upon the digestive organs, for the disposition of forming calculi is always, more or less, accompanied with the indications of deranged digestion; and it is probable that the first link of the series of actions, which cause this disposition, has its origin in the stomach.

The alkaline carbonates are found to answer as effectually as the pure alkalies, and they have the advantage of being less liable to disagree with the stomach. Mr. Hatchett has proposed the carbonate of magnesia, in doses of ℈j to ʒj, as a valuable substitute for alkaline remedies in cases of lithic calculi; but as its insolubility must render its absorption equivocal, the beneficial operation of the substance must principally depend upon its neutralizing any excess of acid in the primæ viæ, and in this way there can be no doubt of its lithonthryptic agency; “but,” says Dr. Marcet, “such is the tendency which the public has to over-rate the utility of a new practice, or to take a mistaken view of its proper application, that there is every reason to believe that the use of magnesia has of late years become a frequent source of evil in calculous complaints.” Lime-water has been also recommended for the purpose of fulfilling the same indications, and as not being liable to produce that irritability of stomach which frequently attends the long continued use of the fixed alkalies; besides which, some chemists have maintained that it exerts a peculiar solvent power over the cementing animal matter of the concretion, and thereby destroys its cohesion.^[207]

Where an acid is indicated, the Muriatic will in my judgment be found as convenient and effectual as any that can be administered. Mr. Brande proposes Cream of Tartar for this purpose; upon this point I differ with him, for this salt, to say the least of it, is questionable in its mode of operation; for although its first impression upon the stomach is that of an acid, the subsequent processes of digestion decompose it, and eliminate its base, which being absorbed acts upon the urinary organs as an alkali. I have seen a white sabulous deposit, consisting of the Phosphates, in the urine of persons after the constant use of Imperial as a beverage, which I am at a loss to explain upon any other principle. Sir Gilbert Blane has also very satisfactorily shewn, that a fixed alkali produces the same effect upon the urinary organs whether it be exhibited alone, or in combination with citric acid; in this latter case the salt undoubtedly undergoes a decomposition in transitu, as I have more fully explained under the consideration of Diuretics, (page 94.) During an alterative course of Lithonthryptic remedies it may be beneficial to interpose occasionally a purgative medicine, but we must not combine it with the lithonthryptic, at least, if we wish this latter medicine to reach the urinary passages; for it is a law which I have already attempted to establish (see page 94), that Catharsis suspends the process of alimentary absorption.

124There remains to be considered another mode of applying a solvent, and which would seem on the first view of the subject to be full of promise,—that of injecting the proposed menstruum into the bladder. Unfortunately, however, the irritable state of this organ will generally preclude the possibility of preserving the menstruum, for a sufficient length of time, in contact with the calculus to accomplish any material solution; nor am I aware that any case, in favour of such a practice, stands recorded. An ingenious and novel application of the powers of Electro-chemistry has been lately^[208] proposed by M M. Prevost and Dumas, as capable of affording means for the solution of the calculus within the bladder; the suggestion is highly plausible, and ought not to be hastily rejected without trial. Could the functions of the part be protected against the influence of so powerful an agent, it is evident that, by a galvanic battery of sufficient intensity, a calculus composed of alkaline or earthy salts might be transferred from the bladder by the simple introduction of a double sound, communicating on one hand with the calculus, and, on the other, with two vessels filled with water, in which are plunged the opposite poles of a galvanic apparatus.^[209] This arrangement would transfer the acid constituents into the vessel connected with the positive end, and the bases into that of the negative end. So far, however, as the experiments have hitherto been carried, this degree of galvanic operation would seem to excite too much irritation in the bladder to be admissible; but it still offers a resource of an apparently more practicable nature. This consists in giving to the calculus a tendency to crumble from the slightest force; such a friability, in short, as shall render it easily broken into pieces sufficiently small to be evacuated through the urethra, especially by the aid of dilating that passage, an operation upon which much has lately been said and written. A fusible calculus from the human subject was submitted to the action of a pile, consisting of 120 pairs of plates, for twelve hours in succession. The platinum wires, constituting the poles, were placed in contact with the calculus, about six or eight lines distant from each other, and the whole plunged in a vessel filled with pure water. During the galvanic action, the bases and phosphoric acid first arrived at their respective poles, then re-entered into combination, when the salt thus reformed was precipitated in the state of powder. The calculus weighed 92 grains before the experiment, and was reduced at its termination to 80. The process being continued, at the end of sixteen hours it presented a mass of such friable texture as to be reduced into small crystalline particles by the slightest pressure; the largest of which did not exceed the size of a lentil, so that it might have easily passed through the urethra.

In order to ascertain how far this decomposition could be effected in the living body, the ingenious experimentalists selected a dog of rather large size, into whose bladder they introduced a fusible calculus attached to a sound, and between two conductors of platinum; the bladder was next distended by injecting tepid water, and the apparatus subjected to galvanic influence. After a little struggling, the animal became calm, and was subjected to the operation during an hour. On removing the sound, the calculus shewed unequivocal marks of decomposition. The same process was repeated, night and morning, during six days, when the friability of 125the calculus rendered it impossible to continue the experiment. It had lost weight in the same proportion as in the preceding trial. The bladder, which was afterwards examined, exhibited no appearance of injury or disease.^[210] The authors assert that this organ does not suffer any inconvenience from this more moderate degree of galvanic action, and suggest, as a proof of the mildness of its influence, that we should immerse the tongue in a vessel filled with water, in which a calculus is undergoing decomposition, and it will be found that the tongue, which is far more sensible than the bladder, will scarcely perceive the galvanic action, even when decomposition is going on briskly. The authors add, that this process cannot offer any advantage for the removal of those calculi which consist wholly of Uric acid, or which contain a large proportion of it.^[211]

ANTIDOTES.

Synon: Alexipharmics. Alexiterials. Counter-poisons.

Medicines which are capable of preventing the ill effects of a poison; or, of counteracting its fatal virulence.

There is perhaps no subject upon which the credulity of mankind has been so extravagantly exercised as on that of Poisons; nor is there, certainly, any class of remedies whose history has suffered so many vicissitudes from the caprice of hypothesis, as that of Antidotes.^[212]

It is not my intention, on the present occasion,^[213] to enumerate the many extraordinary virtues^[214] which credulity has, at different times, assigned to such medicines; nor shall I consume the time of the reader by attempting to expose the absurdity of those fearful powers with which ignorance, terror, and imposture, have invested certain poisons,—a subtlety so extreme as to defeat the most skilful caution, and a virulence so manageable as to be capable of the most accurate graduation; so that while the former attribute was believed to ensure their deadly operation, although exerted through the most secret and least suspicious medium, as that of gloves,^[215] tapers, or letters, the latter was said to enable the accomplished 126assassin to measure the allotted moments of his victim with the nicest precision, and to occasion his death at any period that might best answer the objects of the assassination.^[216]

The abandonment of such notions may be considered as one among the many advantages which have arisen to medicine, from the cultivation of physiology.

Without farther introduction, I shall proceed to the main object of this work, and inquire how far a chemical agent may be capable of neutralizing, or of decomposing, a poisonous substance in the human body; and endeavour to ascertain the degree of confidence to which it may in each particular case be entitled; equally important is it to learn, whether certain vital agents may not be serviceable in cases of poisoning, either by promoting the elimination of the poison, or by producing a state of the system best calculated to resist its deleterious operation.

It may be safely asserted that we possess very few true antidotes; for although several of the mineral poisons may be neutralized or decomposed by various reagents, yet their destructive action is generally so rapid, that the mischief is effected before any chemical changes can avail; and, in other cases, the substances resulting from the chemical action, are as poisonous as the original ingredients, as in the case of the decomposition of Corrosive Sublimate, by the alkalies and earths, when the precipitated oxide is as virulent as the original salt; while, under certain circumstances, I suspect that the vital powers of the stomach are in direct opposition to those changes and decompositions which so readily, and so uniformly, take place in our laboratories. To vital agents then, the practitioner must principally look for succour; but before we can establish any general rules for the treatment of poisoning, it is essential to distinguish between the different modes in which poisonous substances produce their effects, or at least to determine the parts of the living system through which they act; for it will be found, that each poison has its own modus operandi, from which alone can be derived the particular indications of cure.

The hypotheses devised by the ancient physicians, to account for the destructive powers of these substances, were principally derived from mechanical notions respecting the supposed form of their particles, which they imagined capable of lacerating and disuniting the animal fibres by the sharpness of their spiculæ;^[217] it is however, now satisfactorily established 127that the action of a poison in the human stomach is very rarely, if ever, mechanical; sometimes chemical; but for the most part vital in its operation.

Each of the three kingdoms of Nature furnishes a number of poisons, the investigation of whose chemical properties and physiological actions, and that of the symptoms to which their administration gives rise, the lesions of structure which they occasion, and of the medical treatment which they require, constitutes an elaborate branch of science designated by the term Toxicology, and of which I have more fully treated in my work on Medical Jurisprudence.

Poisons differ materially from each other, not only with respect to the modes in which they produce their effects in relation to the several vital organs, but with respect to their application; some of those, for instance, which, if introduced into a wound, are speedily fatal, may be taken into the stomach with complete impunity, as in the instance of the venom of the viper and other snakes, which appears to exert no influence on the stomach; others, on the contrary, display their deleterious action on the stomach alone, such as caustic acids, and alkalies, corrosive sublimate, and some chemical poisons; while others, again, are equally destructive whether applied to the inner surface of the stomach, or to the lower intestines, in the form of clyster, or even to the mucous membrane of the mouth or nose; to the eye; to the vagina and orifice of the uterus, or to an abraded portion of the skin. There is, moreover, a class of substances which may be termed Aerial poisons, for they may exist in the state of gas, or be held dissolved in the atmosphere, and be received by respiration, or by the mucous membranes of the nose and throat; the saliva may also thus become the medium for transferring various subtile poisons from the atmosphere to the animal body; this is well illustrated by the fact of the transfer of metallic influence, as related in the case of a gentleman in perfect health who became salivated in consequence of sitting for one hour by the side of a person who was in a state of mercurial ptyalism, in order to give him a lesson in botany.

It also deserves notice, that a poison acts with different degrees of force and celerity in different parts of the same tissue; its absorption, for instance, would appear to be energetic in proportion to the number of veins,^[218] 128although several apparent exceptions to this law might be adduced, and it is evident that the plethoric state of the part with respect to its blood-vessels has a considerable share in modifying the effects; this observation, however, has no relation to those poisons which operate on the system through the sympathetic communication of the nerves; Mr. Brodie, for instance, found that the poison of bitter almonds acted more speedily when applied to the tongue than when injected into the intestine, though the latter presents a much better absorbing surface.

Foderé, in the fourth volume of his Medicine Legale, arranges poisons according to their action on the living system, and which, with a slight alteration in the order of the classes, has been adopted by Orfila, and most other writers on Toxicology. Poisons are thus reduced into six classes: viz. 1. Corrosive or Escharotic, as the Preparations of Mercury, Arsenic, Antimony, Copper, Tin, Zinc, Silver, Gold, and Bismuth; the concentrated Acids, and caustic Alkalies, and Earths; Cantharides; glass and enamel powder; diamond dust.^[219] 2. Astringent Poisons, of which the preparations of Lead constitute the only species. 3. Acrid or Rubefacient Poisons, which, with a few exceptions, are furnished by the vegetable kingdom, as certain drastic purgatives, Hellebore, Euphorbium, &c. 4. Narcotic Poisons, Opium, Henbane, the Cherry-laurel, Stramonium, &c. 5. Narcotico-Acrid, embracing such articles as produce the united effects of the two former, and which constitute some of the most deadly poisons, as the Ticunas, Nux-vomica, Belladonna, Tobacco, Hemlock, Digitalis, &c. 6. Septic Poisons, contagious miasmata, putrid exhalations from animal matter, Sulphuretted Hydrogen, the venom of the viper, &c.

The value of this classification has been very justly stated to consist in its combining to a certain degree, the advantages of a pathological arrangement with those of one founded on the basis of Natural History; for, while it is strictly pathological, it at the same time distributes the different poisons, with some few and unimportant exceptions, in an order corresponding with that of their natural history. The First two classes, for instance, present us with substances of a mineral origin; the Third 129and Fourth, with those which are chiefly of a vegetable nature; and the Sixth, with objects principally belonging to the animal kingdom. The importance of acknowledging a division, which has a reference to the organic and inorganic kingdoms of Nature, is considerable in a chemical point of view; for in enumerating the various experiments to be instituted for the detection of poisons, we are thus enabled to bring together a connected series of processes, nearly allied to, intimately connected with, and in some respects mutually dependent upon, each other. At the same time it must be acknowledged, that this classification has many defects and some fallacies. In the first place, it has little or no reference to the enlarged views of the modern physiologist, respecting the “modus operandi” of Poisons; nor indeed is its construction susceptible of such modifications and improvements, as can ever render its degree of perfection progressive with the advancement of science. In the next place, the classes are in many particulars ill defined, and indistinctly, if not erroneously, divided. How questionable, for instance, are the boundaries which separate Corrosive from Acrid poisons? the respective species, even, of each class are, in many cases, less allied to each other, than are the great divisions to which they are subordinate. As an exemplification of this fact we have only to compare the physiological actions of Arsenic and Corrosive Sublimate, both of which are arranged under the class of Corrosive Poisons. The former of these substances undoubtedly occasions death by being absorbed, and thus acting as a vital agent; the latter, by its local action, as a caustic on the textures with which it immediately comes into contact. In the same manner, if we examine the individual actions of the different species composing the class of “Acrid Poisons,” we shall discover the same want of uniformity; thus, the Spurge Flax, and the Iatropa Curcas, act by occasioning a local inflammation, while the Hellebore, being rapidly absorbed, exerts a fatal action on the nervous system, and produces only a very slight inflammation. The class of Narcotic Poisons is certainly more absolute in its definition, and more uniform in its physiological affinities, and therefore less objectionable than the divisions to which we have just alluded; but the propriety of the class “Narcotico-Acrid” is by no means equally unexceptionable; indeed Orfila himself questions it, “because the narcotic or sedative effects only follow the previous excitement.” Some of the poisons of this division also are rapidly absorbed, and act, through the medium of the circulation, on the nervous system, without producing any local inflammation; while others, on the contrary, merely act upon the extremities of the nerves, with which they come in contact, and, without being absorbed, occasion death by a species of sympathetic action.

These few objections, and many more might be urged, are sufficient to demonstrate the imperfection of the classification under consideration, and which must render it wholly unavailable to the physician in the treatment of cases of poisoning, who must derive his plan of cure from the physiological action of the substance against which he has to contend; thus, for instance, Arsenic and Corrosive Sublimate are both corrosive poisons, but so materially do they differ from each other in their physiological actions that, when swallowed, they will require for the preservation of the individual, a very different system of treatment.

For such reasons I have ventured to propose a new arrangement of Poisons, which may furnish the practitioner with a general theorem for the administration of Antidotes.

130

A SYNOPTICAL TABLE OF POISONS,

NEWLY ARRANGED

According to the different Primary Operations, by which they produce their effects,

With a view to furnish a General Theorem for the administration of Antidotes.

CLASS I. Poisons which act Primarily, through the medium of the Nerves, without being absorbed; or exciting Local Inflammation.

Order 1. By which the functions of the Nervous System are suspended, or destroyed.

(Death by Suffocation from paralysis of the Respiratory muscles.)

Alcohol.

Aconite.

Oil of Tobacco.

Essential Oil of Almonds.^[220]

Camphor.^[220]

Opium?^[220]

Salts of Lead?

Croton Tiglium.^[221]

Order 2. By which the heart is rendered insensible to the Stimulus of the Blood.

(Death by Syncope.)

Infusion of Tobacco.

Upas Antiar.

CLASS II. Poisons which, by entering the Circulation, act through that medium, with different degrees of energy, on the Heart, Brain, and Alimentary Canal.

(Death in many forms.)

Arsenic.

Emetic Tartar.

Muriate of Baryta.

Hellebore.

Savine.

Meadow Saffron.

Squill.

Opium?^[221]

Lettuce.

Henbane.

Prussic Acid.

Deadly Nightshade.^[221]

Hemlock.

Camphor.^[221]

Coculus Indicus.

CLASS III. Poisons which, through the medium of the Circulation, expend their energies upon the Spinal Marrow, without directly involving the functions of the Brain.

(Death by Tetanic Convulsions.)

Nux Vomica—and the whole tribe of Strychnus.

CLASS IV. Poisons which produce a direct local action on the Mucous Membrane of the Alimentary Canal.

(Death by Gangrene.)

Corrosive Sublimate.^[220]

Verdigris.

Muriate and

Oxide of Tin.

Sulphate of Zinc.

Nitrate of Silver.

Concentrated Acids.

Caustic Alkalies.

Cantharides.

Bryony.

Elaterium.

Euphorbium.

Colocynth.

Hedge Hyssop.

Ranunculi.

Nitre.

131The First Class of our arrangement comprehends such poisons as operate, through the medium of the nerves, upon the organs immediately subservient to life; in their application it is obvious that they cannot require to be introduced into the stomach; they may convey their destructive influence by an application to any part duly supplied with nerves, and whose extremities are exposed to their action. It had been long admitted that a poison might occasion death, by acting on the nerves of the stomach and intestines without being absorbed; but to the experimental labours of Mr. Brodie^[222] we are principally indebted for our present correct views of the subject. The class admits of two important divisions, into one comprehending those poisons which destroy the functions of the brain, and into another, including those which direct their influence upon the heart. We shall offer a few observations upon the facts which have suggested such a division, and upon the practical advantages which may attend its adoption.

It was observed by Bichât, and the observation has been fully confirmed by Brodie, that the influence of the brain is not directly necessary to the action of the heart; and is immediately necessary to life, only because the muscles of respiration owe their action to its influence.^[223] For when the functions of the brain are destroyed, even when the head is removed, the heart continues to contract for some time afterwards, and then ceases only in consequence of the suspension of respiration, which is under the direct influence of the brain. Assuming this as a fact, it will appear evident that certain poisons may, by affecting the brain, so paralyse the muscles of respiration as to occasion death by suffocation, and by such a mode of operation I imagine that those substances, arranged in the former division of my first class, prove mortal. Mr. Brodie accordingly found that, by the administration of a large dose of alcohol to a rabbit, the pupils of its eyes became dilated, the extremities convulsed, and the respiration laborious, and that this latter function was gradually performed at longer and longer intervals, and that it at length entirely ceased. Two minutes after the apparent death of the animal, he opened the thorax, and found the heart acting with moderate force and frequency, circulating dark coloured blood; he then introduced a tube into the trachea, and produced artificial respiration by inflating the lungs, and he found that by these means the action of the heart might be kept up to the natural standard, as in an animal from whom the head is removed. The same phenomena resulted from the injection of two drops of the Essential Oil of Bitter Almonds, diffused in half an ounce of water, into the rectum of a cat; and from the application of the empyreumatic oil of Tobacco to the tongue, and rectum of cats and dogs. Now it is obvious that the functions of the brain are 132immediately disordered by the influence of these poisons on the tongue, stomach, and lower bowels of animals, so instantaneously, that it is impossible absorption should have already taken place.

Although the general proposition seems to be established, that the brain is not immediately necessary to the action of the heart, yet it must not lead us to the conclusion that the heart is therefore incapable of being affected by violent impressions on the nervous system; the fact is quite otherwise, for although the brain may be removed, and the circulation be nevertheless maintained by artificial respiration, yet an injury of another kind inflicted on the brain, may be followed by those immediately fatal consequences which decapitation itself would not produce; thus is a blow on the head commonly followed by syncope, and there are certain poisons that would seem to act in the same manner, such is the Infusion of Tobacco,^[224] which suspends the action of the heart long before the animal ceases to respire, and kills by producing syncope, although in this latter case it has been questioned whether the spinal marrow may not be primarily affected, which has been shewn by recent experiments to have an intimate relation with the action of the heart. Be this as it may, it is sufficiently obvious, that the second division of the first class is sanctioned by theory, and confirmed by experiment.

We come now to speak of the Second Class,—of those Poisons which enter the circulation, and act through that medium on the heart, brain, and alimentary canal. These organs, however, are affected in very different degrees by different poisons, or even by the same poisons, under different circumstances. Mr. Brodie has shewn that vegetable poison, although when introduced into the alimentary canal affect life, in consequence of the nervous sympathy which subsists between these surfaces and the common sensorium, yet, that the same poisons applied externally to a wound, produce their effects exclusively through the medium of the circulation, being conveyed to the brain only by mixing with the blood in its vessels, and not by being conveyed through the lymphatics, for a ligature upon the great blood-vessels prevents their producing deleterious effects; whereas a ligature upon the thoracic duct, or general canal through which all the absorbents pour their contents into the blood, does not in the least retard or prevent the operation of the poison. There are also several of the mineral poisons which, whether introduced into the stomach, or applied externally to a wound, poison the animal in consequence of being carried into the circulation. It had long been supposed that Arsenic occasioned death by inflaming the stomach; but Mr. Brodie has very satisfactorily shewn that its influence arises from its absorption, and that it must be regarded rather as a vital, than as a chemical agent. In the first place, he has found the inflammation of the stomach, in several cases, so 133slight, that on a superficial examination it might have been easily overlooked; and, in most of his experiments with Arsenic, death took place in too short a time to be considered as the result of inflammation; and in the next place, in whatever manner the poison is applied, whether externally to a wound, or internally to the membrane of the stomach, the inflammation is confined to the stomach and intestines; and, indeed, it is commonly more violent, and even more immediate, when applied to a wound, than when internally administered; and it also precedes any inflammation of the wound. This important fact was proved by an experiment made by Mr. Hunter and Sir Everard Home, and subsequently by the repeated investigations of Mr. Brodie.

It has been just stated that after a poison has found its way into the circulation, it expends its virulence upon some particular organs. In some cases this is much more striking than in others. The preparations of Baryta, and of Tartarized Antimony, attack the heart, and occasion death by syncope. Arsenic is less definite in its action, it influences both the brain and the heart, but with different degrees of force in different cases, so that it is often difficult to ascertain which of these organs is the first to fail in its functions. Hydro-cyanic Acid is absorbed, and destroys life by its action upon the nervous system, whose energies it would seem to extinguish without any ostensible injury to the respiration and circulation; for in all those animals which were killed by it in the experiments of Orfila, Brodie, and others, the heart was found acting regularly, and circulating dark-coloured blood; and in some cases, this phenomenon was visible for many minutes after the animal was in other respects apparently dead.

Some substances would seem to direct their powers to various parts of the alimentary canal; and the appearance so produced might be mistaken for the effects of the local action of the poison, had they not been clearly proved by experiment to have arisen from an application addressed through the medium of the circulation; thus is inflammation of the primæ viæ induced by the contact of Arsenic with an external surface of the body!

The Third Class of my arrangement includes those poisons which enter the circulation, and, through that medium, expend their influence upon the spinal marrow, without directly involving the functions of the brain. M. Majendie, in the year 1809, submitted to the first class of the French Institute a series of experiments which had conducted him to the extraordinary result above stated. He found that an entire class of vegetables (the bitter Strychnus) possesses this singular property.

The Fourth Class comprehends all those substances which destroy life by a local action upon the alimentary canal, not by any impression upon their nerves, but by simply inducing a fatal lesion in the membranes.

Through one or more of the above modes of operation all poisons may be said to produce their fatal effects. In some cases a poisonous substance will be found to act in several different ways; thus, the Nightshade is evidently absorbed, carried into the circulation, and is enabled, through that medium to act upon the brain; at the same time it exerts a local action upon the stomach, although less violent than that occasioned by the acrid poisons; it moreover would appear, upon some occasions, to act directly through the medium of the nerves, like those substances 134which have been received in our first class, or else, how shall we explain the fact of the pupil of the eye becoming permanently dilated by the contact of the Belladonna with the tunica conjunctiva? It would appear therefore that this plant unites within itself all the three great modes of action, upon which I have just attempted to establish a physiological arrangement of Poisons. So again, Corrosive Sublimate, although placed in the fourth division, as being a substance which destroys by inflicting local mischief, is nevertheless capable of being absorbed. The embarrassments, however, which might be supposed to arise from this double mode of operation, are of but trifling importance. It is to the primary operation of a poison to which we are to direct our attention, the subsequent effects are less important in as much as they are more capable of being controlled.

Having thus offered a summary of our present views respecting the physiological action of Poisons, we are prepared to lay down a general plan of treatment, which, it will be seen, can only be successful when conducted on principles strictly conformable with the just notions which the preceding experiments have so satisfactorily established.

Where a poisonous substance has, either through accident or design, found its way into the alimentary canal, three important indications are, if possible, to be fulfilled; and under these heads I shall offer such observations as may serve to instruct the practitioner in the philosophy of the general treatment, reserving the details to be observed in that of each poison, for more particular notice in a subsequent part of the work, where the history of these substances will be individually considered. The indications to which I allude are the following, viz.

1. The immediate ejectment of the poison from the body, by the operation of vomiting and purging.

Whatever may be the nature of the poison, we should endeavour with all possible expedition, to eject it from the body; and upon the promptness with which this is effected, the safety of the patient will generally depend; for the dangerous effects of such substances advance in a very increasing ratio, with the time they remain in contact with a living surface. A question may arise, whether in some cases it would not be judicious to attempt in the first instance the neutralization or decomposition of the poison; where a mineral acid, or a caustic alkali has been swallowed, it would undoubtedly be right to neutralize, and dilute it, as soon as possible, and then to excite vomiting, which may be advantageously effected by thrusting the finger down the throat, or by tickling the internal fauces with a feather: where an emetic is at hand, whatever may be its nature, it should be promptly given, but if circumstances will allow us the opportunity of selection, Antimony, Ipecacuanha, &c. should be rejected, and Sulphate of Zinc, or Sulphate of Copper, for several reasons, be preferred; in the first place they do not require much dilution^[225] for their action, a circumstance of no small importance in the treatment of poisons that act by being absorbed; in the next place, they are extremely expeditious, a dose of fifteen or twenty grains producing almost instantaneous vomiting, without 135exciting that previous stage of nausea which so frequently characterises other emetics, and which occasions a state of the vascular system highly favourable to the function of absorption, (as I have so fully explained at page 86, &c.)

The practice of emptying the stomach by means of a syringe, as proposed by Boerhaave, has lately been revived with all the confidence of a new invention. There are cases of narcotic poisoning in which there can be no doubt it would furnish the practitioner with a valuable resource, but I much fear that it will be found to be less successful than its more sanguine advocates have anticipated; for where the stomach has so far lost its power as to be insensible to the stimulus of a potent emetic, the chances of recovery are small; the practice, however, in such cases ought never to be neglected, for it cannot possibly do harm, and may perhaps be beneficial.

After all has been ejected, which the operations of art can effect, we are to proceed, without delay, to the fulfilment of the second indication; viz.

2. The Decomposition of any remaining Portion, and the adoption of measures best calculated to obviate its absorption.

Where the substance is in a solid form, and acts by absorption, we should be very cautious how we favour its solution; while, if it exists in a liquid state, our object must be to render its active portion insoluble; this problem involves a series of questions which are wholly chemical. In order to prevent, or retard, the absorption of the active matter, we must, to a great degree, depend upon the agency of vital adjuvants; this latter indication however does not apply to Corrosive Sublimate and other substances which act upon the stomach locally, and are not absorbed; copious dilution also, in such cases, will frequently disarm the poison of its virulence,^[226] but it should be followed as quickly as possible by vomiting. In cases where the poison requires to be absorbed, before it can display its energies, it would be generally unsafe to administer any solvent. Nothing therefore can be less true as an aphorism, nor more dangerous as a precept, than the unqualified assertion of Boerhaave, “Aqua omnia venena enervat, quæ cum aqua misceri possunt.” (Prælect. in Instit: T. vi. p. 289.) Alkaline solutions and Magnesia, in cases of the ingestion of arsenic, accelerate its fatal effects, by promoting its solution,^[227] whereas Lime, or its Carbonate, has as an opposite tendency,^[228] in consequence of the insolubility 136of Arsenite of Lime; so again, Orfila has shewn that the pernicious qualities of the Muriate of Baryta are counteracted by the administration of any soluble Sulphate, which renders the former substance insoluble. In cases where Verdegris has been swallowed, the administration of vinegar greatly increases its virulence, as M. Drouard has ascertained, by converting the substance into a soluble acetate of copper. This view of the subject will explain why the pure earth Baryta is so slow, and comparatively inert, in its effects upon the system, while its muriate is distinguished by the extreme rapidity and virulence with which it operates. The propriety of administering vinegar, lemonade, and different acid potations, in order to counteract the baneful effects of Opium, which has been so often questioned, will thus also receive ample explanation; it must appear that, if any quantity of the substance of opium remain in the primæ viæ, acid, or mucilaginous drinks will, by favouring its solution and absorption, accelerate its fatal effects;^[229] but should it have been previously ejected from the stomach, that then the anti-narcotic influence of a vegetable acid^[230] may remove the consecutive stupor and delirium, and thus realize the expectations which Virgil has so poetically raised.

“Media fert tristes succos tardumque saporem

Felicis Mali: quo non præsentius ullum

(Pocula si quando sævæ infecere novercæ

Miscueruntque herbas, et non innoxia verba)

Auxilium venit, ac membris agit atra venena.”

“Nor be the Citron, Media’s boast unsung,

Though harsh the juice, and ling’ring on the tongue.

When the drug’d bowl mid witching curses brew’d

Wastes the pale youth by step-dame hate pursu’d,

Its powerful aid unbinds the mutter’d spell

And frees the victim from the draught of hell.”

Chardin, in his travels through Persia, informs us that when a Persian finds himself in a distressed situation, he has recourse to a piece of opium as large as the thumb, and that immediately afterwards he drinks a glassful of vinegar; by which he is thrown into a fit of laughter, terminating in convulsions and death.

With regard to the use of Antidotes, it has been already stated how little they are to be depended upon; in certain cases, however, we are bound to acknowledge their power, but they should be very rarely trusted, unless subsequent to, or in conjunction with, the operation of an emetic; in many cases the effects of this latter remedy may be promoted by the ingestion of liquids holding the particular antidote in solution, a practice which offers the double advantage of accelerating the elimination of the poison, and at the same time of decomposing any which may remain. Orfila has fully established the fact of Albumen being a counter-poison to Corrosive Sublimate; 137vomiting may therefore be very judiciously promoted in cases of such poisoning by water holding the white of egg in solution; with equal effect, where Verdegris has been swallowed, sugared water may be used as a diluent to encourage emesis; and Muriate of Soda in solution will be found the most efficient antidote to Nitrate of Silver; and Sulphate of Magnesia to Acetate of Lead. Where an emetic salt, like Tartarized Antimony, has been taken, copious dilution with common water will in general so provoke vomiting, as to render it its own antidote; but it may be useful to remember, that the Infusion of Galls, and according to Berthollet, the Decoctions of Bark, at the temperature of from 30° to 40° Fah. have the power of decomposing it; while Orfila considers milk the most efficient counter-poison to the Sulphate of Zinc.

Having ejected from the stomach all the poisonous matter we can by vomiting, and attempted to decompose what remains, we are to pursue such measures as may be calculated to prevent the absorption of the poison into the circulation; it has been already observed that on this account nauseating emetics should be avoided; the reader is now requested to refer to our exposé of the celebrated doctrine of Majendie, (page 86, note) and he will see that Venesection proves one of the most powerful means of exciting the function of absorption; hence in poisoning by arsenic, such an expedient should never be recommended,^[231] while a particle of that substance remains in the body; where Corrosive Sublimate has been swallowed, the same precaution is unnecessary. The last indication which remains to be fulfilled is—

3. To anticipate the occurrence of the Consecutive Phœnomena, and to combat them by appropriate treatment.

This is to be conducted on the general principles of Therapeutics; the treatment must necessarily vary in each particular case. Where the exhaustion of nervous energy is to be feared, as after poisoning by Prussic Acid, ammonia, and other diffusible stimulants, together with external warmth, will furnish the best resource; for the same reason Venesection should be performed with great caution and judgment after a narcotic poison. Where, on the other hand, inflammatory action is to be anticipated, it is unnecessary to detail the plan of treatment which may be adopted with the greatest chance of success. In cases where the nervous system is stupified, the symptoms may be combated by vegetable acids, infusion of coffee, &c. but where it is in a state of præternatural excitement, recourse must be had to opiates.

ESCHAROTICS:^[232]

Substances whose application to the animal solids, erodes, or decomposes them.

138The operation of these bodies may, in general, be considered chemical; for having destroyed the life of the part to which they are applied, they cause, as if by a species of resulting affinity, the elements of the animal matter to enter into a new state of combination; this is well exemplified in the action of caustic potass, where the nascent elements thus disengaged by the decomposition of the animal substance, reunite in proportions to generate an oily matter, which may be observed to form a film over the ulcerated surface, while the excess of nitrogen and hydrogen constitute ammonia, which is disengaged during the action of the caustic; and may be rendered sensible by inverting over the surface, a small jar moistened with muriatic acid, when the fumes of Muriate of Ammonia become visible.^[233]

Their surgical value consists in their power to remove excrescencies, to establish an ulcer, or to convert an ulcerated surface into a simple sore.

IV. OF MECHANICAL REMEDIES.

This subdivision includes those classes of remedies, whose operation depends entirely upon mechanical principles; and we must agree with Dr. Murray in considering them as the least important of all the articles which we have enumerated, and which cannot therefore constitute objects of elaborate inquiry.

ANTHELMINTICS:

Remedies which expel worms^[234] from the intestinal canal.

It has been already stated, (page 90) that certain bodies have the power of increasing the peristaltic motions of the intestinal canal, by operating as mechanical stimulants upon its fibres; in this manner the filings of tin and iron, or the irritating down which covers the pods of the Dolichos Pruriens, are supposed to act in dislodging and evacuating the worms from the intestines. But there is a variety of remedies employed as vermifuges, which must owe their effects to a very different mode of operation; Bitters for instance appear to prove an absolute poison^[235] to these animals, while they, at the same time, give an increased tone to the organs of digestion; from whose debility the generation of worms would seem to arise. Other remedies, again, obviously depend upon their simple cathartic property, for the powers which they possess in the evacuation of worms. See Terebinthinæ Oleum—Cambogia.

139In the cure of Ascarides the local application of the remedy becomes necessary, in the form of glyster, and which acts both mechanically in washing out the gut, and medicinally in proving obnoxious to the animals. According to the experience of some of our best practitioners, a strong decoction of the Semina Santonici proves most efficacious upon these occasions.

DEMULCENTS:

Medicines which are capable of shielding sensible surfaces from the action of acrid matter, by involving it in a mild and viscid medium.

It cannot be denied that where these remedies admit of direct application, considerable benefit may arise; in the progress of a catarrh, we have all experienced the relief that may be occasioned by lubricating the fauces with demulcents, which, by soothing the top of the trachea, quiets, by a kind of contiguous sympathy, the whole pulmonary structure; in certain states of intestinal irritation, the same remedies have furnished considerable benefit, and in ophthalmia, relief has been obtained by the application of a demulcent to the inflamed conjunctiva, by which it is defended from the irritation of the tears; see also Formula 61; but in parts beyond the reach of the first passages, and to which no fluid can arrive but through the medium of the secretions, it is very difficult to explain the principle upon which their beneficial operation can depend; and it seems indeed highly probable that they act in such cases as simple diluents, for the process of digestion must necessarily deprive them of their characteristic viscidity. The administration of demulcent drinks in gonorrhæa is probably of no farther service in assuaging the ardor urinæ, than an equivalent quantity of pure water; although Dr. Murray observes, “it is sufficiently certain, that many substances, which undergo the process of digestion, are afterwards separated in their entire state from the blood, by particular secreting organs; and there is, continues he, no gland which has this power more particularly than the kidneys; substances received into the stomach and digested, afterwards passing off in the urine with all their peculiar properties.” This is undoubtedly very true, but mucilaginous substances rarely or never pass off in this manner; if they evade the assimilative functions, they pass through the alimentary canal, and are thus eliminated. I can state, as the result of experiment, that the urine undergoes no change except in the relative proportion of its water, by the copious and repeated administration of mild mucilages. Dr. Saunders has very justly remarked that the long list of Ptisans, Decoctions, &c. usually prescribed upon these occasions, generally owe their virtues to the watery diluent itself.

The pharmaceutical applications of this class of medicines constitute, perhaps, not the least part of their value, by which we are enabled to introduce acrid substances into the stomach with safety and effect; but such services will more properly fall under our notice in a future part of the work.

DILUENTS:

Watery liquors, which increase the fluidity of the blood, and render several of the secreted and excreted fluids less viscid.

There are certainly few remedies whose operation is more simple, obvious, 140or important; and yet there are scarcely any whose value has been more mistaken, or whose application has been so frequently perverted through the suggestions of false theory; water is the universal beverage of animals, and the necessity of its supply is indicated by thirst, a sensation which in excess, is borne with less tranquillity even than that of hunger; in certain morbid states of the body its presence is to be regarded as indicating the necessity of copious potation; and yet how often has the prejudiced physician, under such circumstances, aggravated the pressure of disease, by adding the sufferings of Tantalus. In febrile affections, the irritation of thirst tends to keep up the disease, and hence diluents, besides the other beneficial effects which they may produce, must be regarded as important remedies. There are also diseases of the alimentary canal which may be removed by the same agents; when water is conveyed into the intestines it will have a tendency, by mixing with, and diluting the biliary secretion, to diminish its acrimony, and thus to obviate a source of morbid irritation; the dilution of the chyme and chyle may also have a salutary tendency, and favour the absorption of the finer and more nutritive parts of the lacteals; and by increasing the fluidity of the mass, expedite the numerous combinations which it is destined to undergo. The blood itself is also thus modified in its fluidity; although it has been very truly observed that in healthy bodies, or such as are without any obstruction of the excretions, an unusual distension of the vessels cannot be produced, or at least long subsist; for it is evident that such an increased quantity of water in the blood will immediately pass off by one or other of the excretions; this effect, however, in itself, renders the operation of diluents of signal service in the treatment of the disease; in consequence, for instance, of their disposition to pass off by urine, they furnish valuable resources in diseases of the urinary organs, allaying the pain of strangury, and the irritation from an inflamed bladder. From these observations, the practitioner will be led to appreciate the value of diluents; and many of the beneficial effects which are daily experienced from the copious potation of mineral waters, are, without doubt, to be wholly attributed to simple dilution. See Aqua.

It is here necessary to say a few words upon the misapplication of this order of remedies. Dr. Davy found by experiment that when an animal is bled to death, the last portions of blood that flow are of a much lower specific gravity than that which flows first, in consequence of the former containing more water, which it may be inferred was derived by the increased activity of the absorbents, exerted chiefly on mucous and serous membranes. Since then venesection promotes and accelerates absorption,^[236] it is clear that, in inflammatory diseases, where we have recourse to blood-letting, in order to diminish the volume of circulating fluids, we ought not to suffer the patient to indulge in an unrestrained use of liquids, which he eagerly demands to satisfy a thirst which, in all probability, is the natural consequence of increased absorption. In such cases, it is often better to take liquids in small divided doses, which will have the effect of moderating the thirst, without overloading the arterial system, and bringing on that tension and plenitude which are liable to be produced by swallowing too large a proportion of liquids.