The purport of the following pages is an endeavour to reduce the facts belonging to Animal Life into claffes, orders, genera, and fpecies; and, by comparing them with each other, to unravel the theory of difeafes. It happened, perhaps unfortunately for the inquirers into the knowledge of difeafes, that other fciences had received improvement previous to their own; whence, inftead of comparing the properties belonging to animated nature with each other, they, idly ingenious, bufied themfelves in attempting to explain the laws of life by thofe of mechanifm and chemiftry; they confidered the body as an hydraulic machine, and the fluids as paffing through a feries of chemical changes, forgetting that animation was its effential characteriftic.

The great Creator of all things has infinitely diverfified the works of his hands, but has at the fame time ftamped a certain fimilitude on the features of nature, that demonftrates to us, that the whole is one family of one parent. On this fimilitude is founded all rational analogy; which, fo long as it is concerned in comparing the effential properties of bodies, leads us to many and important difcoveries; but when with licentious activity it links together objects, otherwife difcordant, by fome fanciful fimilitude; it may indeed collect ornaments for wit and poetry, but philofophy and truth recoil from its combinations.