The Action of Medicines in the System. Frederick William Headland
devoted themselves particularly to the study of chemical phenomena are especially prone.
Müller thinks that the agency of many remedies may be explained by their chemical affinities. He supposes that they may effect a change in the nutritive fluids, or that they may so disturb the state of combination in which the elements of an organ may be, that it becomes insensible to the action of morbid stimuli. Some chemists have accounted for the action of Alcohol by its chemical affinity for the brain substance. Liebig considers that the similarity of their composition to that of the brain may serve to explain the operation of such medicines as Quina and Morphia. Such ideas as these are at the best purely hypothetical, and even as theories they seem to me to be untenable—for what reasons I shall have to show when I consider these remedies. Liebig has hazarded several other explanations of a similar kind, of which the following is an example:—"The frightful effects of Sulphuretted Hydrogen and Hydrocyanic Acid are explained by the well-known action of these compounds on those of Iron, when Alkalies are present, and free Alkali is never absent in the blood." (Organic Chemistry, p. 274.) Now in the first place it is not proved that the complete abstraction of iron from the blood would occasion sudden death, though doubtless it is a necessary constituent of that fluid. Further, Prussic Acid acts on the superficial nerves as an Anodyne when applied externally, which it can hardly do by displacing iron. Besides, by parity of reasoning, Ammonia, or Benzoic or Cinnamic Acid, should precipitate iron, if present in the blood in the soluble state, and Sulphuric or Nitric Acid should dissolve it, if in the state of peroxide; and yet none of these agents are frightful poisons. It is not to be imagined that chemical solutions and decompositions of every kind are allowed to take effect in the human system in the same way as in the laboratory of the chemist, for there are in the former many disturbing and controlling causes which suffice to hold them in check.
We may altogether conclude, that though the actions of many remedies may be partly elucidated by chemical considerations, it is impossible to account for the influence of all alike in this way. For at least the actions of nerve-medicines and of gland-medicines cannot be reasonably explained on any such hypothesis.
3. The most plausible explanations of the mode of operation of medicines have been founded on vital or general principles. By vital I mean that these theories concern actions which could only take place in the living body. They may be termed general principles, because the grounds on which they are based are neither mechanical nor chemical, but something different from both. The term dynamical has sometimes been applied to an ill-understood vital action of this sort.
Many different ideas have been broached to account thus for the action of medicines. Some, who have constructed very ingenious and plausible systems, have explained in different ways the operations of different groups of medicines. But when others have adopted a single inflexible hypothesis to account for the action of all alike, this is found, as might be supposed, to be of a very untenable character. I will now consider very briefly several such ideas; first, for the sake of clearness, dividing them into seven sections. I shall explain my meaning as I proceed. Different writers have supposed that the general operation of remedies in the cure of disease is conducted in these various ways.
| a. By degrees of stimulation. |
| b. By counter-stimulation. |
| c. By opposition. |
| d. By similar agencies. |
| e. By elimination. |
| f. By alterative actions. |
| g. By various counteractions. |
a. This idea has received the title of the "Brunonian Theory," from the name of its founder. It was promulgated by the famous Dr. John Brown at the close of the last century. He considered all diseases to arise from excessive or diminished "excitement." He was of opinion that all medicinal agents were stimulants, only that some acted so powerfully as to produce "indirect debility." These latter were to be used in sthenic, the others in asthenic disorders. But it is to be urged against this idea, that many sedatives produce no appreciable degree of "primary stimulation;" that alterative medicines are neither stimulant nor depressent; and that the actions of different therapeutic agents—as, for example, of Opium, Mercury, and Rhubarb—differ very much in quality, and not simply in degree, as Dr. Brown supposed. The principle, then, cannot be maintained.
b. Rasori and other Italians adopted a similar idea about the commencement of this century, only that they supposed two contrary agencies, instead of variations in the degree of the same action, like the Brunonians. Giacomini classified medicines on this plan. The two classes of medicines are termed "Hypersthenics," and "Hyposthenics,"—i.e. Stimulants, and Contra-stimulants, or Sedatives. These were to be used respectively in asthenic and in sthenic disorders. But this idea did not originate with these physicians. It prevails among the modern Hindoos, and seems to have been inculcated by certain medical writers of that nation in very remote times. (On the Hindoo System of Medicine, by Dr. Wise, 1845, p. 213.)
c. The last-mentioned idea supposes only one kind of opposition, and therefore only two descriptions of diseased action. But a much more plausible notion than that is, that each particular disease or symptom is to be cured by administering a remedy which is capable of producing a contrary state. By this contrary condition the disorder is to be neutralized. This was the maxim of Hippocrates—τα εναντια των εναντιων εστιν ιηματα—"contraries are the remedies of contraries." (De Flatibus, par. iii.) On this principle we give purgatives in constipation, opium in diarrhœa, sedatives to relieve pain, sudorifics to combat dryness of skin, etc. etc. But the rule becomes inapplicable when the cause of disease is so complicated that we cannot tell where to find a substance that shall directly oppose its agency. Besides, it cannot in theory be universally applied, for it takes no notice of treatment by evacuation or by revulsion.
d. I am brought now to an idea which is directly opposed to the last. The rule of the disciples of Hahnemann is, "Similia similibus curantur"—or, diseases are to be cured by remedies which shall produce effects similar to them. Now if this were the case, the majority of disorders would be hopelessly incurable. We know of no medicines that are capable of producing such affections as ague, small-pox, or phthisis; and when such remedies are known, their employment would certainly be singularly objectionable. Who would administer Strychnia in tetanus, Opium in congestion of the brain, or irritants in Gastrodynia? The arguments alleged in support of the theory are of the most fallacious kind. For example, it is said that diaphoretics cured the sweating-sickness, and purgatives are given with advantage in diarrhœa, on the "Homœopathic" principle. But it should be observed that the sweating in one case, and diarrhœa in the other, are the attempts of nature to get rid of the disease by eliminating a poison; and that in seconding these attempts we are availing ourselves of an agency which does not resemble the disease, but is like to the natural mode of cure. Such treatment depends, in fact, upon the principle which will have to be considered next in order.
The homœopathists would work a strange revolution in the Materia Medica.[13] Charcoal, Silica, and other substances commonly supposed to be inert, appear as remedies of wonderful efficacy. It is said that Belladonna produces a state like scarlatina, and also a condition resembling hydrophobia, and thus cures both of these disorders. Of these three propositions it is almost needless to say that all are equally erroneous. Further, an experimental trial of this principle was made by Andral on a large number of patients at the Académie in Paris, with the assistance of the homœopathists themselves. The medicines were carefully and fairly administered, but in no one instance were they successful. (Medical Gazette, vol. xv. p. 922.)
e. The idea that diseases are to be cured by assisting nature to eliminate from the system the morbid material, is probably as old as medicine. It was one of the doctrines of Hippocrates; but long even before his time it appears to have been inculcated by a certain sect of old medical writers among the Hindoos. These last were the very earliest advocates of the humoral pathology. (Dr. Wise, op. cit. p. 212.) Dr. Thomas Sydenham, born in 1624, the contemporary of