In the year 1799, Dr. FORDYCE, in a valuable paper published in the second volume of the Transactions of the Medical Society, investigated this subject with much perspicuity and success: unfortunately, however, this memoir terminates with the investigation of _similar_ remedies, that is to say, of those which produce upon the body similar effects, and he is entirely silent upon the advantages which may be obtained by the combination of those medicines which possess _different_, or even _opposite_ qualities; it must be also remembered that at the time this memoir was composed by its eminent author, Chemistry had scarcely extended its illuminating rays into the recesses of physic. Under such circumstances, I am induced to undertake the arduous task of inquiring into the several relations in which each article of a compound formula may be advantageously situated with respect to the others; and I am farther encouraged in this investigation, by a conviction of its practical importance, as well as by feeling that it has hitherto never received the share of attention which it merits. “I think,” says Dr. Powell, “it may be asserted, without fear of contradiction, that no medicine compounded of five or six simple articles, has hitherto had its powers examined in a rational manner.” If this attempt should be the means of directing the attention of future practitioners to the subject, and thereby of rendering the Art of Composition more efficient, by placing it upon the permanent basis of science, I shall feel that I have profitably devoted my time and attention to the most useful of all medical subjects. “_Res est maximi momenti in arte medendi, cum, Formula in se considerata, possit esse profecto mortis vel vitæ sententia._” PHARMACOLOGIA.|| ON THE| OPERATIONS OF MEDICINAL BODIES,| AND ON THE| CLASSIFICATIONS FOUNDED ON THEM. “_Medicos tandem tædet et pudet, diutius garrire de Remediis, Specificis, et Alexipharmicis, et cæteris, nisi eorum naturam et modum quo prosint, quodammodo ostendere et explanare possint._” CONSPECT. MED. THEOR. PHARMACOLOGIA. ON THE OPERATIONS OF MEDICINAL BODIES, AND ON THE CLASSIFICATIONS FOUNDED ON THEM. Medicinal Substances are those bodies, which, by due administration, are capable of producing certain changes in the condition of the living system, whereby its morbid actions may be entirely removed, or advantageously controlled. In adopting this definition we intentionally exclude those alimentary substances which are more immediately subservient to the support of life, and to the repair of that diurnal waste, which the exercise of its functions so inevitably occasions.