- M.uch stress has been laid on this method of ascertaining the effects of medicines, and applying the results so obtained, by analogy, to the human frame. This mode of procedure is, however, open to many objections, and is rendered fallacious in many instances, in consequence not only of differences of the digestive organs, but of the organization of the nervous system. Take the horse, for example: as much as six ounces of Tartar Emetic have been given to horses, without producing any remarkable or permanent derangement of the principal functions; they will take very large quantities of Arsenic with simply the effect of rendering them sleeker and fatter; and they have been known to eat as much as eight pounds of the leaves of the Atropa Belladonna, without any ill consequence. (Moiroud.) The peculiar construction of the stomach or stomachs of the cow, and other animals of the order Ruminantia, renders any deductions drawn from medicines exhibited by mouth to them very little to be relied upon; besides which, it is well-known that some animals will eat with perfect impunity substances which prove poisonous to man.

Introducing substances directly into the circulation, by injecting them into the blood-vessels, has been another means proposed for ascertaining their medicinal effects. Although many useful and valuable physiological facts may be obtained in this manner, the procedure is far from being free from objections; indeed, deductions thus drawn should be received with extreme caution. The very fact of cutting down on a large or deep-seated vessel, and the consequent loss of blood, must influence the result in a therapeutic point of view, setting aside the mechanical effect produced on the circulation and on the nervous system, by the liquid employed as a vehicle for the medicine. The force with which it is injected, and the quantity of fluid used, would also materially influence the result.

Other methods of attaining a knowledge of the therapeutic action of remedies have been proposed; but it would answer no useful or practical end to enter into their consideration.

On the Art of Prescribing Medicines. - Every medical man should pay strict attention to the proper and most efficient manner of prescribing medicines. It is a point intimately connected with his success as a practitioner, and some observations on this subject, so deserving our best attention, cannot be considered otherwise than useful and necessary in a work like the present, having, for its primary object, practical utility.

A prescription is, according to ancient usage, generally described as composed of four constituents, or rather as divided into four parts: - 1, the basis, the principal or most active ingredient;

2, the adjuvans, intended to promote the action of the former;

3, the corrigens, or that designed to correct or modify the operation of the basis; and 4, the excipient or vehicle, which is the substance giving to the former ingredients consistence and form. The following formulae may serve as examples: -

4 Experiments Upon Animals 3

Extracti Colocyntbidis Co.

gr. xxx.

Basis.

Pil. Hydrargyri .........................

gr. x. .

Adjuvans.

Extracti Hyoscyami .................

gr. v. .

Corrigens.

Syrupi q. s. M..........................

Vehicle.

Ft. Pil. xij.

4 Experiments Upon Animals 4

Vini Colchici, fl. drs. ij. ..........................................

Basis.

Sp. Etheris Nitrosi, fl. drm. jss. ..............................

Adjuvans.

Tinct Hyoscyami, fl. drm. j. ....................................

Corrigens.

AquAe, fl. oz. vss., M. ............................................

Vehicle.

Ft. Mist.

It is not, however, necessary that every prescription should be formed on this model; indeed, the fewer the ingredients in a formula the better; it cannot well be too simple. Complexity of prescription should always be avoided; it is generally regarded, with much justice, as a sign of ignorance on the part of the pre-scriber. It is necessary that a prescription should always be written in a legible hand; the symbols denoting the quantities distinctly given: the exact quantity for each dose, the periods for its repetition, and any other directions, should be given at full length, and in the plainest possible language. To this should be added a piece of advice from one of the most practical men of his day, the late Dr. A. T. Thompson, that no prescription should pass from the hand of the prescriber without being deliberately read over, and its correctness ascertained.

The circumstances which modify the action of medicines are very numerous. This modification or alteration depends, in some in-tances, on a peculiarity on the part of the patient; in others, on the character, form, or period of the disease, in which the medicine is administered, on the period of the day at which it is given, on the combination of medicines employed, on the proper regulation of the dose, &c. These, and other points connected with the efficient operation of medicines, merit the attention of every practical man.

Modifying circumstances on the part of the patient: -