Chapter III: Insensible Agents

│ _Specifics._

CLASSIFICATION OF REMEDIES BY DR. MURRAY.

_A._ GENERAL STIMULANTS.

a. _Diffusible._ { _Narcotics._
„ { _Antispasmodics._

b. _Permanent._ { _Tonics._
„ { _Astringents._

_B._ LOCAL STIMULANTS.

_Emetics._
_Cathartics._
_Emmenagogues._
_Diuretics._
_Diaphoretics._
_Expectorants._
_Sialogogues._
_Errhines._
_Epispastics._

_C._ CHEMICAL REMEDIES.

_Refrigerants._
_Antacids._
_Lithontriptics._
_Escharotics._

_D._ MECHANICAL REMEDIES.

_Anthelmintics._
_Demulcents._
_Diluents._
_Emollients._

With respect to the classification of Dr. Cullen, we may commence our objections by stating, that the very basis upon which it rests is a mere gratuitous assumption, viz. _that certain medicines act on the fluids of the body_. With the exception of a very few substances, it is now generally admitted that medicines produce their effects by acting on the living materials of which our organs are composed, and not by modifying the specific gravity, or chemical composition, of the fluids which they may happen to evacuate. The origin of this latter opinion is to be traced to the exploded notions of the humoral pathologists, and to the exclusive doctrine of the earlier chemists; for as the former recognised a depraved condition of the fluids as the source of every disease, so did the latter imagine that every remedy operated by producing a chemical change upon its composition; and the remedial value of a medicinal substance was estimated by its effects upon inert matter. Thus were experiments made with different substances upon the blood, and other fluids of the body, in order to deduce, from the results, the nature and extent of their powers as agents upon the living frame; for instance, the _spirit_ and _salt of hartshorn_, as they were found to render the blood more fluid, when added to it, _out of the body_, were indiscriminately administered in almost every complaint, with a view to dissolve that “lentor of the fluids” which was regarded as the more general source of disease. For similar reasons, a tribe of medicines were introduced into practice under the title of _Antiseptics_, for the prevention of a process which very probably never takes place in the living body: the powers of these supposed agents were, as usual, inferred from their effects in resisting and preventing the putrefaction of dead matter.

Nor is the distinction assumed by Dr. Cullen, between the action of remedies on the _Simple_ and _Living_ solids less hypothetical. Tonics and astringents may certainly exert a beneficial effect upon the animal fibre, but not by any immediate action on its materials, but through the agency of its living principle.—“_Medicamentum non agit in cadaver._”

The classification of Dr. Young, although it presents many points of interest and value, is not altogether free from objection; his classes in some instances are perhaps unnecessarily sub-divided, without a sufficient regard to the primary and secondary operations of the substances which they include. The arrangement of Murray has been adopted in the present inquiry, not as being less objectionable, in a general point of view, but as one which from its simplicity, is better calculated, as a frame-work, if I may so express myself, for the display of those particular facts, the knowledge of which I consider essential for the successful administration of medicinal agents, and for the full comprehension of those practical doctrines which it is the exclusive object of this work to inculcate.

Dr. Murray observes that, in this arrangement, he places in the first division those substances which exert a GENERAL STIMULANT operation on the system. Of this there are two sub-divisions, the DIFFUSIBLE and the PERMANENT; the former including the class of _Narcotics_, with which may be associated, as not very remote in their operation, the class of _Antispasmodics_; the latter comprising two classes, viz. _Tonics and Astringents_. Through these there is a gradual transition from the most highly diffusible stimulant, to those most slow and durable in their action.

A second division comprehends LOCAL STIMULANTS, those, the action of which is determined to particular parts of the system. Such are the classes of _Emetics_, _Cathartics_, _Emmenagogues_, _Diuretics_, _Diaphoretics_, _Expectorants_, and _Sialogogues_; with which may be associated the classes of _Errhines_ and of _Epispastics_, founded on direct local application.

The remaining classes include substances which do not operate according to laws peculiar to the living system. To one division may be referred those, whose effects depend on the CHEMICAL changes they produce in the fluids or solids; the classes which may be established on this principle are _Refrigerants_, _Antacids_, _Lithonthriptics_, and _Escharotics_. To another division belong those, the operation of which is purely MECHANICAL, as _Anthelmintics_, _Demulcents_, _Diluents_, _Emollients_, and certain _Laxatives_.

Under the above classes, says Dr. Murray,[137] may be comprehended all those substances which are capable of producing salutary changes in the human system, and which are used as remedies. I have stated my reasons for adopting this as a general basis of classification, although I shall deviate very considerably in the subordinate divisions of the plan, in the hope of establishing some distinctions that may tend to practical utility.

1. GENERAL STIMULANTS.

The four classes comprehended under this first division, are NARCOTICS, ANTISPASMODICS, TONICS, and ASTRINGENTS.

Although these remedies differ very essentially in the degree and permanence of their action, as well as in the character of their apparent effects, yet, as it is conceived that their _primary_ operation is stimulant, they are considered as possessing sufficient general similitude to sanction their arrangement under one comprehensive division.

NARCOTICS.

Synon: _Sedatives._ _Anodynes._ _Hypnotics._ _Soporifics._

Substances which, in a moderate dose, occasion a temporary increase of the actions of the nervous and vascular systems, but which is followed by a greater depression of the vital powers than is commensurate with the degree of previous excitement, and which is generally followed by sleep.

The relative intensity of these primary and secondary effects varies in the different narcotics,[138] and even in the same narcotic in different doses; in some cases, especially if the quantity administered be considerable, the symptoms of diminished sense and action follow so immediately, that the previous stage of increased action is very obscure, or not in the least perceptible, while in other cases, the operation of the substance is more particularly directed towards the heart and arteries, and syncope succeeds its exhibition. These facts have led many physiologists to deny the stimulant nature of these bodies, and to consider their primary operation as one of a depressing kind, whence they have bestowed upon them the name of SEDATIVES; in referring to the classification of Cullen and Young, we shall find that the arrangement of these substances has been directed in strict conformity with such a view of the subject; but it may be asked, how the increased excitement and exhilaration which so obviously follow the use of these bodies, in small doses, can be reconciled with that theory which considers them as absolutely and primarily sedative? In order to combat an argument so fatal to his hypothesis, Dr. Cullen summons to his aid the potent intercession of his tutelar deity, the _Vis Medicatrix_, a power which he supposes to preside over our living body, and with anxious vigilance, to resist the invasion of every thing that is noxious, or hostile to its health and well being; with such assistance it was not difficult to explain any paradox in physiology, and the anomalies attending the agency of narcotic medicines were accordingly, in the school of Cullen, easily reconciled with the views of a favourite theory. He supposed that whenever a _sedative_ was applied in a moderate dose, the _Vis Medicatrix_ took the alarm, and excited all the powers of the system, in order to throw off the noxious application, and that thus _indirectly_ arose those peculiar symptoms of increased action; but when the dose was more considerable, he contended that the preserving power of the system was silenced, and unable to offer any salutary resistance, and consequently that universal depression immediately followed; but there is no direct evidence in support of the existence of such a power, and still less of its influence upon such occasions; it is far more philosophical to refer the operation of narcotics to a peculiar stimulating power, remarkable for the extreme rapidity with which it exhausts the energy of the nervous system. No one will deny the stimulating powers of alcohol, and yet a very large draught of this liquor will occasion extreme exhaustion without the occurrence of any signs of previous excitement; nor will any one be disposed to question the depressing influence of opium, and yet small doses have enkindled excitement and sustained the powers of life, under circumstances of extreme and alarming exhaustion.[139]

From the celerity with which narcotics produce their effects, it is reasonable to suppose that they act upon the nervous system through the sympathetic relations of the stomach, although in some instances it is highly probable that these bodies are actually absorbed into the circulation; I am inclined to think that this occurs with opium, as death is accelerated in cases of persons poisoned by it, by the adoption of those measures which are best calculated to promote its absorption: (_see Opium_.) A still more striking proof is furnished by the fact of opium, when externally applied to ulcers, producing all its constitutional effects, such as costiveness, head-ache, nausea, &c. Whether the effects of spirituous potations are to be attributed to the introduction of alcohol into the blood, or to the sympathies existing between the stomach and brain, is still a question of doubt. Dr. Cooke[140] relates a case, on the authority of Sir A. Carlisle, of a person who was brought dead into the Westminster Hospital, in consequence of having drank a quart of gin for a wager, and that upon examination, a considerable quantity of a limpid fluid was found within the lateral ventricles of the brain, _distinctly impregnated with gin_. I very well remember the case, for it occurred during the period that I held the situation of Physician to that hospital, but it is very doubtful whether such an absorption occurs under ordinary circumstances. We well know the facility with which certain odorous bodies enter the circulation, and are developed in distant organs; it is therefore very possible that the apparent odour of the gin, which has been sometimes recognized in the secretions, may depend upon the presence of the flavouring ingredients, independent of the alcohol?

At one period, substances supposed to possess narcotic virtues were placed about the bed to obviate watchfulness; the plant _Anethum_, or _Dill_, was very commonly suspended over the head for such a purpose, while in modern times the _Hop_ has been introduced into the pillow.

In concluding the history of Narcotics, it may be observed, that there is, perhaps, no class of medicinal bodies, the individuals of which are less disposed to bend and conform to an artificial arrangement; each would seem to have its own particular mode of operation, and to affect sensibility in its own peculiar manner; and hence the practitioner will often find that, after the failure of one narcotic, the administration of another will induce sleep.

ANTISPASMODICS.

Substances which have the power of allaying the inordinate action of muscular structures, and of assuaging pain, without occasioning that state of insensibility which characterises the operation of narcotics.

There are certain medicinal bodies which would appear to exert a specific control over spasmodic action, from whatever cause it may have originated, such are _Assafœtida_, _Galbanum_, _Musk_, _Castor_, _Ammonia_, _Valerian_, _&c._ To such remedies the term antispasmodic more exclusively belongs, but in a more general view of the subject we must admit that this class branches, by indefinable gradations, into narcotics and tonics; for since spasm may be connected with the most opposite states of the body, it is very evident that many of the individuals included in the class of antispasmodics, can only be relative agents: spasm, for instance, may arise from excessive irritability, as from teething, wounds, worms, &c. in which case a narcotic would prove beneficial; or it may depend upon a state of general debility, the proper remedy for which would be the administration of an Aromatic Stimulant, or the assiduous exhibition of some permanent tonic.

TONICS.

Substances, whose continued administration gives strength and vigour to the body.

It is very justly admitted, that a state of permanent tension in the fibres of the body is necessary for the existence of life, and that any undue departure from such a condition is followed by debility. Thus, Sir Gilbert Blane observes, that no muscle, whether voluntary or involuntary, can act unless its fibres are previously in such a state, that if divided they would shrink by their own resiliency, leaving an interval between the cut extremities; the same may be said of the vascular system in all its ramifications, in order to give play to their contraction in grasping and propelling their contained fluids. It appears that there are certain medicinal bodies that have the power of affecting this state of tension, and when their effects contribute to its restoration, they are properly denominated _Tonics_. We are not, however, to consider them as producing such a change by any mechanical operation upon the matter of which the fibre is composed, but by a direct action upon its living principle; it seems probable that certain poisons may thus produce sudden death by their agency on the vital principle, by which the tension of the heart and whole arterial system is immediately relaxed. In this point of view, _Tonics_, like the other remedies which we have described, may be _relative_ or _absolute_ in their operation. Venesection, purgation, or whatever will, under certain conditions of the body, occasion a salutary change in its vital powers, may produce a corresponding alteration in the tension of its fibres, and consequently fall under the denomination of a tonic remedy: but independent of the state of the body, there would seem to be certain substances that act as specific stimuli upon the living fibre, and are in certain cases indispensable for the maintenance of its healthy tone; such are vegetable bitters, which produce a powerful effect upon the digestive organs, and by nervous sympathy, upon the rest of the system. _Bitter Extractive_,[141] seems to be as essential to the digestion of herbivorous, as salt is to that of carnivorous animals; it acts as a natural stimulant, for it has been shewn by a variety of experiments that it passes through the body without suffering any diminution in its quantity, or change in its nature. No cattle will thrive upon grasses which do not contain a portion of this vegetable principle; this fact has been most satisfactorily proved by the late researches of Mr. Sinclair, gardener to the Duke of Bedford, which are recorded in that magnificent work, the “HORTUS GRAMINEUS WOBURNENSIS.” They shew, that if sheep are fed on _Yellow Turnips_, which contain little or no bitter principle, they instinctively seek for, and greedily devour any provender which may contain it, and if they cannot so obtain it they become diseased and die. We are ourselves conscious of the invigorating effects of slight bitters upon our stomach; and their presence in malt liquors not only tends to diminish the noxious effects of such potations, by counteracting the indirect debility which they are liable to occasion, but even to render them, when taken in moderation, promoters of digestion. The custom of infusing bitter herbs in vinous drinks is very ancient and universal; the _Poculum Absinthiatum_ was regarded in remote ages as a wholesome beverage, and the Wormwood was supposed to act as an antidote against drunkenness. The Swiss peasant cheers himself amidst the frigid solitude of his glaciers, with a spirit distilled from _Gentian_, the extreme bitterness of which is relished with a glee that is quite unintelligible to a more cultivated taste. With regard to the natural use of _Bitter Extractive_, it may be laid down as a truth, that it stimulates the stomach,—corrects putrefying and unwholesome nutriment,—promotes tardy digestion,—increases the nutritive powers of those vegetable substances to which it is united,—and furnishes a natural remedy for the deranged functions of the stomach in particular, and through the sympathetic medium of that organ, for the atony of remote parts in general; and I shall hereafter shew, that in its medicinal applications it certainly imparts additional activity to many remedies, while it renders the stomach and system more susceptible of their salutary energies. As an essential ingredient in the provender of herbivorous animals, it may I think be admitted as a fact, that its importance is _in an inverse ratio_ with the nutritive powers[142] of the food, and we accordingly find, in conformity with that universal scheme of self-adjustment and compensation, which influences all the operations of nature, that cultivation, which extends the nutritive powers of vegetable bodies, generally diminishes their bitterness in the same proportion; the natural history of the Potatoe offers a good illustration of this fact, for the roots of this useful plant which have been so greatly improved by culture, are in their wild state both small and _bitter_.[143] Gummy matter, which seems to result from the first change of the sap, is undoubtedly rendered more digestible and nutritive by the presence of a _bitter_; pure gum is not very much disposed to yield to the assimilative functions; “it frequently passes through the bowels,” says Dr. Chapman,[144] “very little changed, as I have witnessed a thousand times.” We see therefore the value of the bitter principle, in the economy of the _Lichen Islandicus_, which is intended as the food of animals in northern latitudes; we are told that boiled linseed constituted the sole diet of the people of Zealand during a scarcity of long continuance, on which occasion, symptoms of great debility occurred, attended with those of dyspepsia; so again Professor Fritze, in his Medical Annals, states that vegetable mucilage, when used as a principal article of diet, relaxes the organs of digestion, and produces a viscid slimy mucus, and a morbid action in the primæ viæ, an effect which analogy shews might be obviated by the addition of bitter extractive. For the same reason animals that feed in marshy lands, on food containing but little nourishment, are best defended from the diseases they are liable to contract in such situations by the ingestion of bitter plants.[145] Upon these occasions nature is very kind, for the particular situation that engenders endemic diseases is generally congenial to the growth of the plants that operate as antidotes to them.

I have offered these views upon the subject of _Bitter Extractive_, from a conviction that they will essentially contribute to the establishing of just and philosophical notions, respecting the necessity and _modus operandi_ of many vegetable tonics.

As the action of tonics is gradual, so their operation is not followed by that exhaustion consequent upon the use of diffusible stimulants.

The substances which compose the class of tonics are derived from the vegetable and mineral kingdoms; those of the former are generally bitter, and produce their effects by a primary action on the stomach, and are not absorbed into the circulation, as experiments upon _Bitter Extractive_ have most fully demonstrated; those derived from the mineral kingdom, comprehending several of the metals, appear in some instances to pass into the circulation, although several of them, like the vegetable tonics, act primarily on the _primæ viæ_; I apprehend this observation applies to the _nitrate of silver_, which certainly possesses considerable powers as a tonic in certain cases of dyspepsia, for which it may perhaps be indebted to the bitterness which distinguishes it.

AROMATICS.

Substances of a fragrant smell,[146] which produce upon the organs of taste a peculiar sensation of warmth and pungency, and occasion, when swallowed, a corresponding impulse upon the stomach, which is rapidly communicated to the remote parts of the body.

The vegetable bodies which constitute the class of aromatic stimulants are very intimately related with that of tonics; indeed in the most efficient vegetables of the latter kind, the two qualities are generally blended, and the transition from these to the more pure bitters and aromatics is so imperceptible, that it is extremely difficult to arrange them in different classes; Dr. Murray has accordingly in his classification not attempted to separate substances which are so intimately connected. _Aromatic Stimulants_, however, in a practical point of view, must be distinguished from tonics, as the former are valuable for the _rapidity_, the latter, for the _permanency_ of their effects. Their characteristic properties appear to depend chiefly, if not entirely, on an essential oil which, when extracted from the vegetable, exhibits all its aromatic power in a very concentrated form.

Medicines of this kind, when administered for the purpose of dispelling wind from the alimentary canal, have been termed _Carminatives_.[147] They would seem to act by imparting energy to the distended and weakened muscular coat of the stomach, by which the accumulated _gas_ is propelled through the upper orifice; for this viscus, like the bladder, when greatly distended, becomes unable to relieve itself, partly in consequence of the exhausted state of the over-stretched fibres of its muscular coat, and partly perhaps from a contraction of the _Cardia_, or upper orifice; for it has been already stated that a loss of power, and spasmodic action, are often the simultaneous results of debility.

ASTRINGENTS.

Substances which, when applied to the human body, corrugate and condense its fibres, and at the same time, exert a tonic influence through the medium of its living principle.

Astringency in any substance may be at once recognised by the organs of taste; its power in corrugating the papillæ of the tongue, and in imparting a sensation of harshness and roughness to the palate, being too peculiar to be mistaken; this is a fortunate circumstance, for there does not exist any one chemical test by which we can invariably detect the property of astringency, since it is found to reside in many different classes of substances: thus, acids, especially the stronger mineral ones, are powerfully astringent; so are many of the metallic salts, as those of iron, zinc, copper, and lead; and some of the earths, when combined with acids, of which alum is a striking example. The vegetable kingdom, however, furnishes the greater number of astringent remedies; and chemistry has shewn that this property uniformly depends upon a peculiar proximate principle, characterized by its power of forming an insoluble compound with animal gelatine; to this principle the name of TANNIN has been given. As tannin generally exists in union with gallic acid, and as the latter body is known by its property of striking an inky blackness with the salts of iron, solutions of this metal were long, but erroneously, regarded as the proper test of vegetable astringency; the fallacy of this is at once shewn by the habitudes of Catechu, one of the strongest of our astringents, but which, nevertheless, will not yield the smallest degree of blackness to the solutions of iron, because it contains only tannin, the true principle of astringency, without a trace of its usual associate the gallic acid. From the power which these substances possess of astringing, and condensing the animal solids, their medicinal properties are supposed to arise, and we may perhaps, in this instance, admit such a mechanical explanation; but astringents possess also some power over the living principle of the matter which they astringe, for they are capable of acting as permanent stimulants, of curing intermitting fever, and of obviating states of general debility. Astringents would seem to moderate the morbidly increased secretions of distant parts, and to restrain hemorrhage, by their corrugating influence upon the _primæ viæ_,[148] which is extended by sympathetic action to the vascular fibre; it is not difficult for any person to conceive the possibility of such a sympathy, who has ever experienced the thrilling and singular feeling which is produced over the whole body, by the _acerb_ taste of the sloe-juice. As however the primary operation of these bodies, by their actual contact with the animal fibre, must be much more powerful than that which can result from the mere sympathy of parts, we find that the efficacy of astringents is principally displayed in the cure of diarrhœa, or serous evacuations from the intestinal canal; their operation, in checking profuse fluor albus, gleet, and the inordinate secretions of other distant organs, is much less striking and unequivocal, and it is a question whether in many of such cases the benefit arising from their use may not depend upon their tonic powers. As the morbid excess of different evacuations may arise from various and opposite states of the living system, so may the individuals of the other classes become astringents; and we are bound to admit upon this, as we have on other occasions, the existence of _absolute_ and _relative_ remedies.

Narcotics, at the head of which stands opium, will frequently assume the character of astringents, by diminishing the irritability upon which increased discharges depend. In Diarrhœa, an astringent, properly so called, diminishes the flow of those acrid fluids into the intestines, by which their peristaltic motions are præternaturally increased, and it consequently represses the diarrhœa; a narcotic, under similar circumstances, might not repress the flow of the acrid matter to which I have alluded, but it would render the bowels less susceptible to its stimulus, and would therefore produce the same apparent alleviation, although by a very different mode of operation. There is yet a third species of remedy, which may operate in restraining a diarrhœa of this description; not by stopping the flow of acrid matter, nor by diminishing the irritability of the intestinal organs, as in the instances above recited, but, simply, by _acting chemically_ upon the offending matter, so as to disarm it of its acrid qualities; such, for instance, is the nature of _absorbent_ and _testaceous_ medicines. In the cure of hemorrhage, if it be _active_, that is to say, connected with a state of strong tonic contractility of the blood-vessels, a very different remedy will be required as an astringent, than in cases of _passive_ hemorrhage, in which the vascular fibres are in a state of relaxation or collapse. Sir Gilbert Blane has offered some valuable remarks upon this subject, with a view to settle the difference of opinion which has arisen respecting the treatment of flooding after child-birth. (_Medical Logic_, _Edit._ 2d. p. 100.)

Astringents are capable of being exclusively used as local applications, and when they are so employed for the purpose of stopping hemorrhage, they are termed STYPTICS.[149] With respect to these latter agents it must be confessed, that great popular error still exists, much of which has evidently arisen from deductions drawn from the effects of such remedies upon inferior animals; thus have several substances gained the reputation of _Styptics_, from the result which may have followed their application to the wounded and bleeding vessels in the extremities of the horse and ass; whereas the fact is, that the blood-vessels of these animals possess an inherent power of contraction which does not exist in those of man, and to which alone the cessation of the hemorrhage, fallaciously attributed to the _Styptic_, is to be wholly attributed. In many cases an application may owe its styptic qualities to its power of coagulating the blood around the orifice of the wound; in this way the contact of heated metal will sometimes arrest the flow of blood from a cut surface.

LOCAL STIMULANTS.

This Second Division comprehends those medicinal substances, which have been generally classed under the head of EVACUANTS; for, as they stimulate particular organs, so do they occasion by their local operation, an increased secretion, or evacuation from them.

EMETICS.

Substances which excite vomiting, independent of any effect arising from the stimulus of quantity, or of that occasioned by any nauseous taste or flavour.

Before we can determine the _modus operandi_ of emetics, it will be necessary to take an accurate view of the phenomena and pathology of vomiting. It is an important fact that any extraordinary stimulus applied to the stomach, instead of increasing its motions, as it would in other instances, actually inverts them: the wisdom of such a peculiar provision is manifest; it is intended to prevent the protrusion of the food into the duodenum before it has undergone those necessary changes in the stomach, by which it is prepared for the more elaborate process of chylification. The act of vomiting, however, is not effected, as Dr. Haygarth formerly supposed, by the sole influence of the stomach; the brain is an important accessary: Dr. Majendie goes so far as to attribute the operation of vomiting, exclusively, to the agency of this latter organ upon the abdominal muscles, and regards the stomach as a mere passive instrument in the act;[150] this doctrine was supported in an elaborate experimental memoir, presented by this indefatigable physiologist to the Royal Institute of France in the year 1812.

Although we shall not be disposed to receive this theory in its full extent, yet we cannot hesitate to admit that the influence of the nervous system is indispensably necessary for producing vomiting; and we accordingly find that this act will not take place, however forcibly the stomach may be goaded by emetics, where the energy of the nervous system is suspended, as in cases of profound intoxication, or in violent wounds and contusions of the head; while if the brain be only partially influenced, as by incipient intoxication, or by a less violent blow upon the head, its irritability is increased instead of being paralysed, and vomiting under such circumstances is excited by the slightest causes: the fact of such opposite results being produced by the same impulse in different degrees of intensity, is no less curious than instructive. Dr. Richard Harrison, in his Gulstonian Lecture before the College of Physicians, treated the subject of vomiting with much ingenuity, and I am disposed to adopt the views which he offered. He observed, that although the experiments of Majendie sufficiently testify the importance of the pressure of the abdominal muscles upon the stomach in the act of vomiting, and which can only be explained by the influence of the brain and nervous system, yet that he has attributed too much to their agency; “it appears to me,” continued he, “that vomiting may be explained in the following manner:—_the irritation of the stomach makes a call upon the brain for the aid of the diaphragm and the abdominal muscles, in order to expel its contents; the diaphragm then becomes contracted and fixed, the ribs drawn down, and the abdominal muscles drawn inwards, so that the stomach is pressed on all sides by voluntary muscles, which, together_ WITH ITS OWN CONTRACTION, _expel the contents_.” Now it must be obvious that where the brain, from oppression or injury, is unable to transmit its influence to these muscles,[151] and disregards the call of the stomach, vomiting can only be excited with difficulty, or it will be prevented altogether.

Under such circumstances venesection may in some cases prove a powerful adjuvant, by unloading the vessels of the brain, and thus restoring to the nervous system its necessary excitability; where its powers have been paralysed by the operation of a narcotic, a copious draught of some vegetable acid, or the affusion of cold water upon the surface of the body may impart efficiency to an emetic; the operation of _Nightshade_ and some other narcotic poisons may be adduced in farther illustration of this subject;—an excessive dose of the _Atropa Belladonna_ produces symptoms of alarming stupor, and so difficult is it to evacuate the stomach under such circumstances, that as much as fourteen grains of _Tartarized Antimony_ have been administered without effect: now if in such a case a copious draught of some vegetable acid be given, the emetic will be more likely to succeed: here then we perceive, that the brain, being paralysed by a narcotic poison, is unable to lend its aid to the muscles requisite for the operation of vomiting, until its energies are restored by the anti-narcotic powers of a vegetable acid. The practical precaution which this view of the subject affords, is extremely important,—_not to allow the apparently inactive state of the stomach to induce us, inconsiderately, to augment the dose of an emetic:_ for although the stomach, for the reasons just stated, may be unable to void its contents by vomiting, it may nevertheless retain its sensibility, and be therefore liable to inflammation: Dr. Harrison has reported a case of this kind, where the practitioner, in attempting to excite emesis in an epileptic patient, by a very large dose of _sulphate of zinc_, produced an inflammation in the viscus that terminated fatally.

Vomiting may also be produced by the _primary_ operation of certain agents upon the brain, by which its energy is disturbed, as by narcotics, or by the motions of swinging, whirling, and sailing: in such cases, the series of actions necessary for the establishing of vomiting, commences in the brain, and is propagated by nervous sympathy to the stomach.

When an emetic is taken into the stomach, an interval of twenty minutes or longer, usually passes without any apparent effect; an uneasy sensation, which we term nausea, is then felt, and this continues to increase until vomiting begins; here then we perceive are two distinct stages, each of which is marked by its own proper symptoms; the relative intensity and duration of which will be found to vary according to the nature of the exciting causes; thus some Emetics, as _Sulphate of Zinc_, act without occasioning much nausea, while others, as _Tobacco_ excite it to a degree which is far greater than is proportioned to their emetic power: this is a fact of great importance in directing us in the selection of an Emetic, for we shall find that in some diseases it is a great object to avoid that state of system which invariably accompanies nausea, while in others it affords the best mode of answering an important indication of cure.

Nausea would seem to depend upon the exertions of the stomach and muscles, not being proportioned to the effects of the brain, in order to produce vomiting. Where this balance however is maintained, as during the operation of an ordinary emetic, the following are the symptoms which characterise the two stages;—while the nausea only is present, the countenance is pale and shrunken, the pulse feeble, quick, and irregular, and there is a feeling of cold; but as soon as vomiting commences, the face becomes flushed, the pulse quicker and stronger, although it seldom returns to its natural standard, until some time after the vomiting has ceased. A degree of languor, a disposition to sleep, and a general moisture upon the skin, are the circumstances which occur after the total cessation of the paroxysm.

The feeble state of the circulation, as indicated by the pulse, and the general coldness and languor experienced during a paroxysm of nausea, are to be ascribed to those sympathetic relations by which the brain, stomach, and heart, are reciprocally influenced.

The advantages to be obtained from the administration of an emetic in the cure of disease, may either depend upon its _primary_, or _secondary_ operations, that is to say, upon the mere evacuation of the stomach, or upon those changes which occur in distant parts from sympathy; and the judicious practitioner, in the selection of an emetic, will always be guided by the nature of the indication which he intends to fulfil; if his object be to evacuate the stomach quickly and completely, he will avoid those emetics that are distinguished by their nauseating tendency, as in cases of disease which depend on a disordered state of stomach, connected with undue distention, and the presence of acrid and indigestible matter; if, on the other hand, his intention be to influence some remote organ through the sympathetic powers of the stomach, an emetic of an opposite tendency may be better calculated to answer such indications: in some cases, he is to seek a beneficial result from the mechanical action of the diaphragm and abdominal muscles, by whose pressure the gall-bladder and hepatic ducts are emptied of their contents, and hence jaundice, arising from the obstruction of biliary calculi, has been suddenly removed by the _concussion_ of an emetic: a similar pressure upon the thoracic viscera may occasion expectoration, and relieve the bronchial vessels in cases of asthma, catarrh, and croup.

Vomiting, when produced by the operation of a mild emetic, does not appear to exhaust the excitability of the stomach, but on the contrary to increase its tone; for we generally find the process of digestion is carried on more vigorously afterwards; although it is probable that, by frequent repetition, a different result would be obtained, and we should find that its motion would become liable to inversion by slight stimuli: we may therefore question the propriety of that practice which is so strenuously recommended by Hippocrates,[152] and other ancient physicians, to administer emetics frequently to those in health, in order to prevent the incursions of disease.

The benefits arising from the secondary effects of an emetic are numerous and extensive. It has been observed that during nausea the force of the circulation is considerably abated, hence the use of these remedies in hemorrhage; and, as the energy of absorption is generally in an inverse ratio to that of the circulation,[153] we frequently obtain from a nauseating dose of an emetic, considerable assistance in the treatment of anasarca, and other dropsical swellings. Those medicines that are liable to produce at once, full vomiting, without any previous stage of nausea, are of course less calculated to fulfil such indications. In the same manner we should select a _nauseating_ emetic, when our object is to promote the passage of a gall stone through the _ductus communis_, for the nausea so excited will relax the duct, while the mechanical concussion tends to push the obstructing matter forward. On the other hand, whenever our object is to evacuate the stomach, and to prevent absorption, we must take care to cut short the nauseating stage; a precaution which is highly important in the treatment of a case of poisoning. The state of the stomach produced by vomiting is very frequently extended, by sympathy, to the vessels of the skin; in consequence of which, a diaphoresis not unusually follows the operation. In the different varieties of febrile disease, this circumstance stamps additional value upon the class of Emetics; while, at the same time, that they eject any offensive matter which may be present in the stomach, they thus control the accelerated circulation.

From the violent muscular exertions which take place in the act of vomiting, the administration of an emetic may be very injurious in certain states of the body. In consequence of the pressure applied to the descending aorta, and the interrupted circulation through the lungs, from impeded respiration, the blood returns with difficulty from the head during a paroxysm of vomiting, and in plethoric states of the body, or in cases of determination of blood to the cerebral or pulmonary organs, the act of vomiting cannot be considered as free from danger. The concussion of an emetic may also produce mischief in the advanced stage of pregnancy, and in _hernia_ and _prolapsus uteri_; while in extreme debility, there is the danger of a syncope being produced, from which the patient may never recover, as I once witnessed in the last stage of Phthisis, where an emetic was imprudently given, with the intention of dislodging the pus with which the lungs were embarrassed.

By violent and protracted retching, a person will sometimes become jaundiced; the stomach, diaphragm, and abdominal muscles, are, under such repeated efforts, apt to be rendered, to an eminent degree, irritable; so that at each effort of the former to discharge its contents, the latter will frequently be thrown into strong spasmodic contractions, and the liver together with the gall bladder will be suddenly caught, and, as it were, squeezed in a powerful press; in consequence of which the bile will regurgitate, and be carried into the _Venæ cavæ_; for Haller has shewn with what facility a subtle injection, when thrown into the hepatic duct, will escape by the hepatic veins; and upon which Dr. Saunders observes, “I know this to be a fact, for I have ascertained by experiment, that water injected in the same direction, will return by the veins in a full stream, though very little force be used.” When a jaundice is thus produced it will gradually disappear without the aid of any medicine; the kidneys are the principal means by which all unnecessary bodies are extracted from the circulating mass, a portion of bile will therefore under such circumstances be eliminated in every discharge of urine.

The different emetics employed in practice are derived from the vegetable and mineral kingdoms, some of which appear to produce their effects by an immediate impression upon the nerves of the stomach, while others require to be absorbed into the circulation before they display their energies. _Ipecacuanha_ would seem to act primarily on the stomach, but _Tartarized Antimony_ has been found, by experiment, to occasion vomiting, when injected into the veins of an animal; while the other mineral emetics, _viz._ the preparations of _Copper_ and _Zinc_, undoubtedly operate on the stomach, and without inducing much nausea.

CATHARTICS:

Medicines which quicken or increase the evacuation from the intestines, or which, when given in a certain dose, occasion purging.

These remedies, from a general difference in their modes of operation, have been classed under two divisions—LAXATIVES and PURGATIVES. The former operate so mildly that they merely evacuate the contents of the intestines, without occasioning any general excitement in the body, or even stimulating the exhalant vessels of the canal; the latter produce a considerable influx of fluids from these vessels, and extend their stimulant effect to the system in general; and where these effects are very violent, the purgative is further distinguished by the epithet DRASTIC. Laxatives then may be said to empty the bowels simply, and to carry off extraneous matter, which is out of the course of the circulation; but purgatives, as they occasion a constitutional effect, may be made subservient to very important purposes. The effects of a purgative may depend upon three different modes of operation; viz.

1. _By stimulating the muscular fibres of the Intestines, whence
their peristaltic motion is augmented, and the contents of the
bowels more quickly and completely discharged._

2. _By stimulating the exhalent vessels, terminating in the inner
coat of the intestines, and the mouths of the excretory ducts of
the mucous glands; by which an increased flow of serous fluids
takes place from the former, and a more copious discharge of
mucus from the latter; the effect of which is to render the fæcal
matter thinner and more abundant._

3. _By stimulating the neighbouring viscera, as the Liver and
Pancreas, so as to produce a more copious flow of their
secretions into the intestines._

It appears that different purgatives have very different powers in relation to the several modes of operation above specified; some medicines, for example, urge the bowels to evacuate their contents by an imperceptible action upon the muscular fibres, and little or no increase of serous discharge attends the evacuation, such are _Manna_, _Sulphur_, and _Magnesia_; there would seem, moreover, to be certain bodies that have the property of increasing the peristaltic motions by operating as mechanical stimulants upon the fibre; it would not be difficult to derive many illustrations of this fact, from the history of herbivorous quadrupeds, and I have been disposed to consider the harsh and coarse texture which certain grasses assume in moist situations, as a wise provision in Nature to furnish an increased stimulus to the intestines of the animals who feed upon them, at a time when their diminished nutritive qualities must render such a result desirable; but the operation of a mechanical laxative may be demonstrated by a more familiar example; the addition of bran to our bread, constituting what is known by the name of _Brown bread_, induces laxative effects, merely from the mechanical friction of the rough particles, or scales of the bran, upon the inner coats of the intestines, for the wheat without the bran in bread is not particularly laxative.[154] Other cathartics stimulate the fibres to a much greater degree, and the effects are either confined to a part of the canal, or communicated to the whole range of the intestines, from the duodenum to the extremity of the rectum; _Aloes_ will furnish a good example of the former, and _Colocynth_ may be adduced as an instance of the latter mode of operation. Other cathartics, again, direct all their stimulus to the exhalant vessels, and are accordingly distinguished by the force with which they produce serous evacuations; and for which they were formerly denominated _Hydragogues_, such are _Saline Purgatives_, and certain vegetable bodies to be hereafter described. Dr. Cullen has even supposed that some of these medicines may act solely in this way, and without increasing directly the peristaltic motion; there is, however, as Dr. Murray very justly remarks, no proof of such an hypothesis, and it seems scarcely probable that any substance should act as a stimulant on these vessels, without at the same time stimulating the mobile fibres of the intestines. _Mercurial Purgatives_ appear to possess, in an eminent degree, the power of exciting the functions of the liver, and of thereby occasioning an influx of bile into the intestines. From the indications which cathartics are capable of fulfilling, their utility in many diseases must be apparent; the extent of their importance and value were, however, never justly appreciated until the valuable publication of Dr. Hamilton on this subject, in which the author has pointed out with more precision than any preceding writers had done, the therapeutic principles which should regulate their administration. His practice has clearly proved that a state of bowels may exist in many diseases, giving rise to a retention of feculent matter, which will not be obviated by the occasional administration of a purgative, but which requires a continuation of the alvine stimulant, until the healthy action of the bowels is re-established. Since this view of the subject has been adopted, numerous diseases have received alleviation from the use of purgatives that were formerly treated with a different class of remedies, and which were not supposed to have any connection with the state of the alvine evacuations; thus in fever, the peristaltic motion of the intestines is diminished, and their feculent contents are unduly retained, and perhaps, in part, absorbed, becoming of course a source of morbid irritation; this fact has long been understood, and the practice of administering cathartic medicines under such circumstances has been very generally adopted; but until the publication of Dr. Hamilton, physicians were not aware of the necessity of carrying the plan to an extent beyond that of merely emptying the _primæ viæ_, and they did not continue the free use of these remedies through the whole progress of the disease.

Cathartics are essentially serviceable also in several diseases of the class NEUROSES, which are generally intimately connected with a morbid condition of the alimentary passages; _Chorea_ and _Hysteria_ have been very successfully treated in this manner. The diseases incident to puberty in both sexes are also best relieved by a course of purgative medicines, and their effects in _Chlorosis_ have conferred upon many of them the specific title of EMMENAGOGUES.

But the therapeutical utility of Cathartics extends beyond the mere feculent evacuations which they may occasion. In consequence of the stimulating action which some of them exert upon the exhalent vessels, they abstract a considerable portion of fluid from the general current of the circulation, and are, on that account, beneficial as _Anti-phlogistics_. For the same reason they may act as powerful promoters of absorption, for there exists an established relation between the powers of exhalation and absorption, so that when the action of one is increased, that of the other is augmented.

Certain Purgatives, as I have just stated, exert their influence upon the neighbouring organs, and are calculated not only to remove alvine _sordes_, but to detach and eliminate foul congestions from the biliary ducts and pores.

With such facts before us, it is impossible to concede to the opinion of Dr. Hamilton,[155] that the different species of purgative medicines _do not possess distinct powers over the different species of matter to be evacuated_; on the contrary, there is reason for reviving the ancient theory, too inconsiderately abandoned, and which acknowledged these different distinctions in the operations of cathartic medicines, under the appropriate names of _Hydragogues_, _Cholagogues_, &c.

The importance of cathartic medicines having been shewn, and the distinctions in their modes of operation established, it only remains to say a few words upon the subject of their abuse. All the remedies of this class, but more especially those of considerable power, require caution in their administration, even in those diseases where they are indicated by peculiar symptoms, especially if there be any tendency to inflammation, or to extreme debility, although this latter symptom is often rather apparent than real, and is at once removed by the brisk operation upon the bowels; during pregnancy and immediately after delivery, and during the flow of the menses, the prudent practitioner will use a discretionary caution in their exhibition. The too frequent use of these medicines will induce marasmus, and render the bowels so morbidly irritable, that purging is easily excited by the ordinary stimulus of our aliments; while in some habits the contrary obtains, and the resource to which the valetudinarian flies for relief only increases the torpor of the intestines, and confirms his costiveness.

The mode of adapting, combining, and administering Cathartics, will present subjects for our future consideration.

EMMENAGOGUES:

Medicines which are capable of producing the Menstrual discharge.

As Amenorrhœa, or retention of the menses, is generally the effect of a morbid state of the body, it follows that remedies capable of acting as Emmenagogues can only be _relative_ agents, unless indeed we are disposed to accede to the opinion so generally maintained in the writings of the older physicians, but now generally discarded, _that certain substances exert a specific[156] action upon the uterus_. It may certainly be asserted without fear of contradiction, that there are many substances which, when received into the stomach, have their stimulant operation more particularly determined to one part than to another; alkalics, for example, to the kidneys; cantharides to the bladder; mercury to the salivary glands, &c. Reasoning therefore by analogy, it was not unphilosophical to conclude, that similar medicines might exist with respect to the uterus; but experience has negatived the supposition, there being no proof of any of the substances styled _Emmenagogues_ producing their effects by any _specific_ influence upon the uterine system. If the term _Emmenagogue_ be assumed conventionally, according to this view of the subject, it may be retained without any fear of error, otherwise it would be wiser to remove the name from our classification.

The suppression of the catamenia usually depends upon a debilitated state of the body, although it is sometimes the consequence of a plethoric diathesis; in the former cases tonics, in the latter, venesection may display the powers of an emmenagogue; upon which occasion, I have frequently derived the greatest benefit by cupping the patient upon the loins. Where the disease occurs in young women, about the age of puberty, it is very generally connected with extreme debility of the system; the preparations of iron, bark, and other invigorating medicines, are accordingly the most likely to succeed in its cure. Whereas in full florid habits, when the catamenia are suddenly suppressed, _Laxatives_, _Diaphoretics_, or _blood-letting_, afford the surest means of relief.

There are two other classes of medicine which may occasionally prove emmenagogue—ACRID PURGATIVES, which act upon the rectum, and hence by _contiguous sympathy_ upon the uterus, as _Aloes_, &c. and STIMULATING DIURETICS, as _Cantharides_, the _Turpentines_, &c. which are supposed to excite the womb, sympathetically, by their stimulus upon the bladder. Nor is the advantageous influence of mercury to be overlooked, which, in cases of morbid action in the secreting functions, prove a Herculean remedy.

DIURETICS:

Medicines which increase the urinary discharge.

This effect is produced by very different modes of operation; and as some of them are mutually incompatible with each other, it is essential that we should understand the _modus operandi_ of each individual of which the class consists, in order that we may direct its application with precision.

There is undoubtedly no tribe of medicinal agents more precarious in their nature and effects than that of Diuretics; this fact in a great measure depends upon the uncontrollable character of the organs upon which they act, but it must at the same time be admitted, that their failure frequently depends upon their modes of operation being directly incompatible with the state of the system at the time of their administration.

The following classification may perhaps serve to bring together the principal facts which are known upon the subject, and at the same time to display them in an order which is calculated to demonstrate their practical bearings and relations.

DIURETICS,

ARRANGED ACCORDING TO THEIR SUPPOSED MODES OF OPERATION.

CL: I.—MEDICINES WHICH ACT _PRIMARILY_ ON THE URINARY ORGANS.

1. _By stimulating the secreting vessels of the kidneys_, BY
CONTACT.

_a_ The medicines not undergoing any decomposition _in
transitu_.

1. _Potassa._

2. _Potassæ Nitras._

3. _Oleum Terebinthinæ._

4. _Juniperus Communis._

5. _Cantharides._

_b_ The Medicines undergoing decomposition _in transitu_.

1. _Potassæ Acetas._

2. _Potassæ Super-tartras._

3. _Scilla Maritima._

4. _Colchicum Autumnale._

5. _Copaifera Officinalis._

6. _Spartii Cacumina._

CL: II.—MEDICINES WHICH ACT _PRIMARILY_ ON THE ABSORBENTS, AND
_SECONDARILY_ ON THE KIDNEYS.

_Mercury._