3. When medicines of the same class, or even of different classes, are given together, the _strongest_ only produces an effect. But what are we to say to a compound of two medicines which give exactly the same impression to the system? Probably, if we are to judge from analogy, the effect of them will be such as would have been produced by neither, in a simple state. 4. By observing simplicity in your prescriptions, you will always have the command of a greater number of medicines of the _same_ class, which may be used in succession to each other, in proportion as habit renders the system insensible of their action. 5. By using medicines in a simple state you will obtain an exact knowledge of their virtues and doses, and thereby be able to decide upon the numerous and contradictory accounts which exist in our books, of the character of the _same_ medicines. Under this head, I cannot help adding two more directions. 1. Avoid sacrificing too much to the _taste_ of your patients in the preparation of your medicines. The nature of a medicine may be wholly changed by being mixed with sweet substances. The Author of Nature seems to have had a design, in rendering medicines unpalatable. Had they been more agreeable to the taste, they would probably have yielded long ago to the unbounded appetite of man, and by becoming articles of diet, or condiments, have lost their efficacy in diseases. 2. Give as few medicines as possible in tinctures made with distilled spirits. Perhaps there are few cases in which it is safe to exhibit medicines prepared in spirits, in any other form than in _drops_. Many people have been innocently seduced into a love of strong drink, from taking large or frequent doses of bitters, infused in spirits. Let not our profession be reproached in a single instance, with adding to the calamities that have been entailed upon mankind by this dreadful species of intemperance.