Prop. IV.—That some few remedial agents act locally on the mucous surface, either before absorption, or without being absorbed at all. That they are chiefly as follow:— (continued 4)

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

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

Ord. I. General Sedatives.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Ord. II. Special Sedatives.

(Antimonials. Ipecacuanha. Digitalis.)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Prop. IX.—That a third class of medicines, called Astringents, act by passing from the blood to muscular fibre, which they excite to contraction.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Ord. I. Mineral Astringents.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Ord. II. Vegetable Astringents.

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

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

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

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

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

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

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

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

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

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

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

This concludes the list of Astringent medicines.

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

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

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

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

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

Prop. X.—That a fourth class of medicines, called Eliminatives, act by passing out of the blood through the glands, which they excite to the performance of their functions.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

4. Acrid fixed oils.—Such are Castor and Croton Oils; they are Purgatives, passing off by the bowels.

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

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

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

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

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

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

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

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

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

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

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

Ord I. Sialagogues.[45]

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

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

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

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

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

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

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

Ord. II. Expectorants.

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

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

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

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

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

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

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

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

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

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

Ord. III. Cathartics.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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