Altho’ I have not the honour of a personal Acquaintance with you, yet impelled by a desire of being informed on a subject of natural science, and knowing no person upon whose opinion I could place so much reliance, I have taken the liberty of writing to you—

Nor should I now obtrude1 on your time, had I not known that you take pleasure in distributing useful knowledge—

The subject on which I wish to be informed is respecting the classification of animals—Whether with Dr shaw and the British Zoologists you adopt the classification of Linnæus:—whether with the french naturalists you prefer that of M. Cuvier or of M. Blumenbach—whether you have not formed one peculiar2 to yourself—or whether you, with the learned M Buffon reject all classification as injudicious and impracticable—

This opinion of the french naturalist certainly has its analogy—Diseases were formerly divided into classes orders genera species & varieties by Dr Sydenham Dr Cullen and other nosologists; and in fact nosology was adopted by the medical world—But these divisions have been shown to the satisfaction of most pathologists to be injudicious impracticable and even injurious by my illustrius and truly worthy friend and preceptor in medicine Dr Rush; and disease proteiform as it is has been demonstrated to be an unit—But I think notwithstanding the ingenuity and erudition with which M. Buffon has defended his opinion, that the classification of animals stands on a more solid basis—But upon the propriety and manner of classification I must importune your opinion—

While a student of medicine I attended several courses of lectures on natural History in the Museum of Mr Peale by Dr Barton. He adopted the classification of M. Cuvier with some few modifications—

As the nomenclature of the Classes orders genera & even some of the species is highly objectionable—I have attempted to reform it, but have not dared to make it public—

Another subject upon which I wish to consult you is with respect to that curious genus of animals the Ornothorhyncus—I wish to know to what order, or even to what class you assign it: I say to what class; because it [dif]fers materially from the mammalia—[. . .] Home nor no other zootomist who has had an opportunity of desecting them ever find them to possess mammæ—They differ also in other important particulars—It seems to approximate more to the Aves in having the mandibles—Cloaca—and in having a spur on its leg (at least the O. paradoxus) I am ignorant where to give it a place; but am rather inclined to the opinion we shall have to constitute a new class for this anomalous genus—on this subject, however, it becomes me to be silent untill I hear your opinion