128 



CHORDATE ANATOMY 



into a "true teat," as in man, or else by elevating the surrounding ridge 

 to form the "false teat" of ruminants. The number of teats corresponds 

 roughly to the number of young in a litter. 



Certain abnormalities in the milk glands of man, however, confirm 

 strongly the theory of the animal origin of the human body. Super- 

 numerary nipples appear in man with a certain statistical frequency. 

 But these extra teats, instead of being placed at random, are usually set 



Fig. 120. — The presence of supernumerary teats (polymastism) in man supports 

 the theory of the animal origin of the human body. Their repeated occurrence has 

 received no other rational explanation. They are reversions or atavisms. (Redrawn 

 after Wiedersheim.) 



in two ventral rows, precisely like two rows of nipples which form the 

 milk lines of lower mammals. They are, then, best interpreted as rever- 

 sions to an animal ancestor. The theory of special creation gives no 

 clue whatever to their occurrence in human beings. See Fig. 120. 



Functional differences among the glands of vertebrates are much greater 

 than morphological, and their physiological evolution is a difficult problem 

 in biochemistry. 



