Such are the objects which are to be attained by combining several substances in one _Formula_, and such the laws by which these compositions are to be regulated; but unless a physician can satisfactorily trace the operation of each element in his prescription to the accomplishment of one or more of the objects which I have enumerated, SIMPLICITY should be regarded by him as the greatest desideratum. I was once told by a practitioner in the country that the quantity, or rather complexity of the medicines which he gave his patients, for there never was any deficiency in the former, was always increased in a ratio with the obscurity of their cases; “if,” said he, “I fire a great profusion of shot, it is very extraordinary if some do not hit the mark.” Sir Gilbert Blane[275] has given us a similar anecdote; “a practitioner being asked by his patient why he put so many ingredients into his prescription, is said to have answered more facetiously than philosophically, _in order that the disease may take which it likes best_.” A patient in the hands of such a practitioner has not a much better chance than the Chinese Mandarin who, upon being attacked with any disorder, calls in twelve or more physicians, and swallows in one mixture all the potions which each separately prescribes! Let not the young practitioner however be so deceived; he should remember that unless he be well acquainted with the mutual actions which bodies exert upon each other, and upon the living system, it may be laid down as an axiom, that _in proportion as he complicates a medicine, he does but multiply the chances of its failure_. SUPERFLUA NUNQUAM NON NOCENT: let him cherish this maxim in his remembrance, and in forming compounds, always discard from them every element which has not its mode of action clearly defined, and as thoroughly understood. The perfection of a Medicinal Prescription may be defined by three words; it should be PRECISE (in its _directions_,) CONCISE (in its _construction_,) DECISIVE (in its _operation_.) It should carry upon its very face an air of energy and decision, and speak intelligibly the indications which it is to fulfil. It may be laid down as a position which is not in much danger of being controverted, that _where the intention of a medicinal compound is obscure, its operation will be imbecile_. A Medicinal Formula has been divided into four constituent parts, a division which will be found to admit of useful application to practice, in as much as it was evidently suggested with a view of accomplishing the more prominent objects which have been related in the preceding pages; or, in the language of Asclepiades, of enabling the BASIS to operate “CITO,” “TUTO,” et “JUCUNDE.” Quickly, Safely, and Pleasantly—thus I. THE BASIS, or Principal Medicine. (_curare._) II. THE ADJUVANS; that which assists and promotes its operation. (“_Cito._”)