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PART II.

T H E

MATERIA MEDICA.

PiITERS on the materia medica have taken greatpains in arranging the various articles, of which it iscompofed, into different divifions and fubdivilions,according to their real or reputed medicinal powers.

It has been imagined, that " the whole materia medica is re-' ducible under the three diminutions of alte-atives, evacuanU, and'• rtjioratives : the firft comprehending all that has any power to" alter the conftitution, without fenfibly increafing or diminifh-4 mg any of the natural evacuations; the fecond, whatever vifi-" bly promotes thofe difcharges ; and the third, all that contributes" t0 ' e '^ en them, arid make the increase greater than the wafte."fhefe divifions being too general, they are broken into fubdivifions;a nd thefe again are farther divided into different claffes, undermore retrained denominations, as cardiac, carminative, hytieric,"omachic, &c.

Specious as this plan may appear to he, I am afraid that theexecution of it, to any ufeful purpofe, would require a far moreex ten five knowledge of the nature and operation of medicinesman h»s yet been attained to. A juft and ufeful method of fim-p'ies is fcarcely to be expedited, whiie thofe properties, on which'he method is founded, are imperfe£tly known, and in many arti-cles only conjed\ural.

In all the arguments that have been hitherto contrived uponthis plan, there appears a ftriking incongruity among the feveralarticles of which even the ultimate fubdivifions are compoied ; fub-ftances extremely diffimilar being claffed together, as cantharidesand tea, tobacco and bran, hemlock and cowllips, fcurvygrafs andfaifins, arum root and liquorice, wormwood and parfneps, cinna-mon and nettles, rafberies and chalk, artichokes and alum, clovesand coffee, muflard feed and black cherries, &c. Nor are thefeincongruities to be laid always to the charge of the authors; the

nature