PROGRESS OF SYSTEMATIC ZOOLOGY. 381 



ture, we may take Man for our type 3 , as being 

 best known to us ; and the remainder of the first 

 Book is occupied with a description of man's body, 

 beginning from the head, and proceeding to the 

 extremities. 



In the next Book, (from which are taken the 

 principal passages in which his modern commenta- 

 tors detect his system,) he proceeds to compare the 

 differences of parts in different animals, according 

 to the order which he had observed in man. In the 

 first chapter he speaks of the head and neck of 

 animals ; in the second, of the parts analogous to 

 arms and hands; in the third, of the breast and 

 paps, and so on ; and thus he comes, in the seventh 

 chapter, to the legs, feet, and toes; and in the 

 eleventh, to the teeth, and so to other parts. 



The construction of a classification consists in 

 the selection of certain parts, as those which shall 

 eminently and peculiarly determine the place of 

 each species in our arrangement. It is clear, there- 

 fore, that such an enumeration of differences as we 

 have described, supposing it complete, contains the 

 materials of all possible classifications. But we can 

 with no more propriety say that the author of such 

 an enumeration of differences is the author of any 

 classification which can be made by means of them, 

 than we can say that a man who writes down the 

 whole alphabet writes down the solution of a given 

 riddle or the answer to a particular question. 



3 Lib. i. c. iii. 



