232 ZOOLOGICAL ACCEPTATION OF 



ther, but because it has red pupils ; and the analogy of nu- 

 merous other instances induces me to regard all the other 

 mammalia, which are destitute of the colouring pigment of 

 the eye, as varieties degenerated from their original stocks*." 



This method is the only satisfactory one of investigating 

 the varieties of the human species. The diversities of phy- 

 sical and moral endowment which characterize the various 

 races of man, must be analogous in their nature, causes, and 

 origin, to those which are observed in the rest of the animal 

 creation ; and must therefore be explained on the same 

 principles. 



There is no point of difference between the several races 

 of mankind, which has not been found to arise, in at least 

 an equal degree, among other animals, as a mere variety, 

 from the usual causes of degeneration. Our instances are 

 drawn chiefly from the domesticated kinds, which, by their 

 association with man, lead an unnatural kind of life, are 

 taken into new climates and situations, and exposed to va- 

 rious other circumstances, altogether different from their 

 original destination. Hence they run into varieties of 

 form, size, proportions, colour, disposition, faculties; which, 

 when they are established as permanent breeds, would be 

 considered, by a person uninformed on these subjects, to be 

 originally different species. Wild animals, on the contrary, 

 remaining constantly in the state for which they were origi- 

 nally framed, retain permanently their first character. 



Man cannot be called, in the ordinary sense of the term, 

 a domesticated animal; yet he is eminently domestic. In- 

 habiting every climate and soil, acted on by the greatest 

 variety of external agencies, using every kind of food, and 

 following every mode of life, he must be exposed still more 

 than any animal to the causes of degeneration. 



I proceed to consider the circumstances in which the 

 several races of men differ from each other, to compare them 

 to the corresponding differences of animals, and to shew 

 that the particular and general results of these inquiries 



* De Gen. Hum. Far. Nat. p. 70, 71. 



