Elements of materia medica and therapeutics; including the recent discoveries and analysis of medicines / [Anthony Todd Thomson].

  • Thomson, Anthony Todd, 1778-1849.
Date:
1835
Catalogue details

Licence: Public Domain Mark

Credit: Elements of materia medica and therapeutics; including the recent discoveries and analysis of medicines / [Anthony Todd Thomson]. Source: Wellcome Collection.

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    16 CHEMICAL ACTION OF MEDICINES. or of the means employed by the physician. Medicines also operate in this manner and change the seat of irritation, setting up, as it were, a new centre of morbid perceptions; and, ac¬ cording to the law of the system, by increasing the sensibility of one part, we diminish that of neighbouring parts, and the blood is directed in greater quantity to the part thus acted upon ; or, in the language of the ancients, a revulsion is produced. The beneficial effects of many medicinal agents can be readily explained upon this principle ; as, for instance, those of rubefacients, vesicants, and escharotics: thus, an incipient in¬ flammation of the tonsils is often rapidly removed by the appli¬ cation of a liniment, composed of Ammonia and a fixed Oil, to the fore part of the neck: an attack of gout in the stomach, by the application of boiling water to the pit of the stomach : and deep-seated pains, by the operation of caloric in the form of the actual cautery. But the benefit of counterirritant action is not confined to external applications. The advantages derived from the use of purgatives, in affections of the head and chest, are justly referred to their counterirritant influence: even sudori- fics and diuretics operate as revulsives, and the benefit derived from their employment is the result of the same counterirrita¬ tion, set up on the skin, and in the kidneys. This mode of action is employed for one of two purposes: either to change the irritation or excitement from the viscera to the skin; or to transfer it from the viscera of one cavity to those of another. But much caution is requisite in the employment of this description of medicinal action : it may augment the general excitement to a degree sufficient to aggravate rather than to diminish the disease for which it is employed. Thus, as I shall particularly prove, in treating of vesicants, the ap¬ plication of blisters so considerably quickens, and so much in¬ creases the force of the general circulation, that they are unfit remedies in the early stage of extensive acute inflammation. It is, however, necessary to distinguish between this state of excitement and that general irritability of the system, which is often accompanied with fugacious pains, and a small, quick pulse; in which the application of a local remedy, acting upon the prin¬ ciple now under consideration, seems to bring the irritation, as it were, into a focus, and thus to relieve the system. /. CHEMICAL ACTION OF MEDICINES. Medicines sometimes operate by combining chemically either with the substance of the body itself, or with the contents of the stomach and the first passages. 1. Some medicines when applied to the surface of the body enter into chemical union with the animal matter of the skin,