The Action of Medicines in the System. Frederick William Headland
to construct myself, as it is with the mode of operation of medicines that I am particularly concerned. The chief and obvious objection to such a classification consists in the insufficiency or insecurity of the data which we have to guide us. Thus the best and safest way is to select as the bases of primary subdivision those distinctions which admit of being the most readily and firmly established, and not to rest it on a number of uncertain or questionable hypotheses.
I. Opinions concerning the ultimate Effect of Medicines, and Classifications founded on this.
Most authors have grouped remedies together according to the broad results of their action. They do not make inquiry as to the mode of operation or behaviour of a medicine after passage into the system; nor do they ask whether this action is especially directed to any organ or tissue; but they judge by external evidence of its ultimate effect on the body, and on the powers of life.
There is commonly a tendency to describe all medicines under two heads, as either causing or diminishing vital activity. Dr. Murray indeed confounds these two effects, and adopts an idea on this subject which was originated by Mr. Brown. I shall now represent in an abridged form the classifications adopted severally by Dr. Young, Dr. Duncan, and Dr. Murray.
| Dr. Young | ||
| 1. Chemical Agents. | ||
| Caustics, etc. | ||
| 2. Vital Agents. | ||
| A. Supporting strength. Nutrients. | ||
| B. Causing action. (Partial and transitory.) Stimulants, Irritants, Astrigents, Alteratives, Evacuants. (Permanent.) Tonics. | ||
| C. Diminishing action or sensation. (Primarily.) Narcotics, Nauseants, Sedatives, Diaphoretics. (Secondarily.) Exhaurients. | ||
| 3. Insensible Agents. | ||
| Specifics. | ||
In the names of these three classes some reference is made to the modus operandi of medicines, but the distinctions thus attempted to be drawn are of the slenderest possible description. Among chemical agents are included some that are applied externally, and act then on the tissues in obedience to known chemical laws. But how can we affirm that some medicines passing into the stomach may not operate chemically? The term vital signifies little; and the word insensible, applied to the third class, is a confession of absolute ignorance. It does not attach to a medicine any distinctive character to say that we know nothing of its operation. Pursuing the subdivision further, we find that the distinctions are not well maintained. Tonics support strength as well as cause action; and it can hardly be said that the action of an Alterative, such as mercury, is partial and transitory. It seems unwise to have made a separate class of Specifics. They are especially associated with Alteratives. Mercury, Iodine, and others, would fall under both groups. Of Evacuants it may be observed, that they are also Exhaurient, and thus included in two opposed classes; that their action is not always partial and transitory, as, for example, Purgatives may permanently remedy constipation; and that it seems wrong to have separated Diaphoretics from them.
Thus neither the primary nor the secondary subdivisions of this arrangement can be reasonably maintained in theory, and we must fall back on the ultimate groups which are based upon common experience. From this failure we may infer that the idea that medicines differ prominently in causing or diminishing vital activity, upon which idea this and many other arrangements are founded, is in fact an erroneous one. There is no such universal distinction. A medicine which at one time raises or excites the vital forces, may at another time depress them; it may do one thing with a sick man, the other thing with a healthy man; it may have the one effect when taken for a short time in moderation, the other effect when taken for a long time or in excess. In fine, the result of the operation of a medicine does not necessarily depend upon this alternative. Although there are undoubtedly some medicines which tend to stimulate the nervous forces, and others which tend to depress them, yet as there are many remedies which may operate well without doing either the one or the other, and whose operation does not depend at all upon this, the distinction cannot be generally applied.
The next arrangement, that of Dr. Duncan, appears, as far as it extends, to be correct in theory. If some additions were made to it, it would be a tolerably perfect classification of this kind. Assuming as a basis the ultimate or practical effect of medicines, we may proceed to divide them into groups in a natural way. Food and liquids are of use in the nutrition of the tissues, and will form the first class. A second set of substances act so as to expel from the body certain humours and secretions. Another class exalt the tone of the nervous system, and through it stimulate the system at large. A fourth set depress the same. And a fifth group do none of these things; but their action results in certain obvious changes in the chemical nature of the secretions.
| Dr. Duncan | ||
| Alimenta. | ||
| Diluentia, Demulcentia | ||
| Evacuantia. | ||
| Diaphoretica, Errhina, Expectorantia, Cathartica, etc. | ||
| Stimulantia. | ||
| Topica (irritants, etc.) | ||
| Generalia permanentia. | ||
| Generalia transitoria. | ||
| Deprimentia. | ||
| Refrigerantia, Narcotica. | ||
| Chemica. | ||
| Acida, Alkalina. | ||
As far as it extends, this classification seems to be founded on correct data. The smaller divisions are natural. Thus Evacuants are grouped according to the part of the system at which the evacuation is made. General Stimulants are divided into those which are transitory in action, and those whose effect is permanent, as Tonics. Dr. Duncan is concerned only with the ultimate effect, and enters into no theory respecting the action of Tonics. I regard them as medicines acting primarily in the blood, and, applying my terms with a view to the modus operandi, I would restrict the term Stimulant to medicines acting on the nerves, whose effect is transitory.
The great fault of this arrangement is the omission of the very important class of Alteratives. We have medicines which increase secretion; medicines which exalt or diminish the vital energy; but where are the remedies which act in the blood? Where, for example, shall we place such medicines as Mercury, Arsenic, and Iodine, which neither act by eliminating, nor by stimulating, nor by depressing, but appear to counteract in the blood the agency of certain morbid poisons? In an arrangement founded on ultimate effect, they should be grouped in a class as Alteratives, as medicines which result in altering for the better the condition of the system. Both Dr. Duncan and Dr. Murray seem to have thought that no medicines could act in the fluids but such as have a well known chemical effect upon them. It cannot be that medicines should be able to affect the nerves, and to influence the glands, in divers ways, but that none should exert any action upon the blood, a most susceptible and changeable fluid, the medium of nutrition, the source of all the tissues, the "fons et origo" of disease. It is only very lately that authors have begun to recognise and include in their arrangements the class of blood-medicines, which seem to me to be considerably more important than any other.
Having shown thus what appear to me to be the correct bases upon which an arrangement of this kind should be constructed, I shall quote as another specimen the classification of Dr. John Murray, but mentioning only its most prominent details.
| Dr. Murray. | ||
| General Stimulants. | ||