Note 251 — ON THE THEORY AND ART OF PRESCRIBING.

If the facts stated in this section be true, we are bound to recognise two orders of medicinal elements,—the one comprehending those that possess an inherent and independent activity,—the other, those that are in themselves inert, but which are capable of imparting impulse and increased energy to the former when combined with them. As this is a new view of the subject of vegetable combinations, no apology is necessary for the introduction of new terms for its explanation; I therefore propose to designate the former of these Substantive, and the latter, Adjective constituents. When the structure of vegetable remedies shall have been thoroughly examined upon this principle of combination, much medicinal obscurity will be removed, and probably some pharmaceutical improvements of value suggested; at all events it will teach a lesson of prudent caution to the pharmaceutic chemist; it will shew the danger of his removing this or that element from a vegetable compound, merely because he finds, upon its separation, that it is inert. I dwell the more upon this point, because I feel that there never was a period in the history of medicine, at which such a caution was more necessary; for while the poly-pharmacy of our ancestors has driven the physician of the present day into a simplicity of prescription that on many occasions abridges his powers and resources, the progress of chemical knowledge has diffused through the class of manufacturing chemists a bold spirit of adventure and empiricism,—a mischievous propensity to torture our best remedies, in order to concentrate or extract the parts which they consider to constitute their essential ingredients.

A Memoir has lately been presented to the Philomatic Society of Paris, by M. Robiquet, on the subject of Aroma, which affords some important analogies in proof of the law of combination, which I am now endeavouring to elucidate. From the experiments of this laborious chemist it would appear, that odours are not as Fourcroy supposed, the effect of the simple solution of certain bodies in air, but that for their developement, some third body (coinciding in its office with my Adjective constituent) possessing in itself none of the characteristic odour, is absolutely necessary as an intermede, varying in its nature according to that of each odorous body, in the same way that the mordant requires to be varied by the dyer, according to the nature of the colouring matter which it is intended to fix on the cloth;—thus Ambergris has in itself very little odour, but the addition of Musk developes a very strong and decided one; this also happens in a less degree with Lavender, and the perfumers therefore add a small quantity of musk to the distilled water of this plant. In other cases, Ammonia lends, as it were, its volatility to bodies, the odour of which without such an auxiliary, would be scarcely sensible; this is exemplified by the practice of perfumers exposing their musk and other substances to the atmosphere of privies when they lose their power: (Paul Amman: Manduct: ad Mat: Med:) so again in order to give pungency to snuff it is made to suffer the commencement of fermentation, in which case ammonia is generated; and it is a curious fact that the odour of the best snuff may be destroyed by mixing with it a little tartaric acid, by which its ammoniacal salt is neutralized. In some instances the adjective ingredient seems to be Sulphur, as in the essential oils of some cruciform plants, and particularly in that of mustard seed, for M. Robiquet found that this oil lost its odour by being kept in contact with a metallic surface, and that an inodorous oil remained, while the metal became a sulphuret: perhaps, adds M. Robiquet, it may be sometimes necessary for the full and exquisite developement of odour in these bodies to add another vehicle, thus the addition of a little Acetic acid heightens the odour of Mustard.

Iron has little, or no odour; but when volatilized with hydrogen, its odour is very powerful. The smell of copper and brass must depend upon some circumstance not well understood.