EVOLUTION AS SEEN IN SEROLOGICAL TESTS 



111 



cates that a smaller amount of precipitate is formed in this tube than was 

 formed in the other two. Evidently, then, baboon serum contains some pro- 

 teins similar to those in human serum; presumably, however, the greater 

 proportion of the baboon's serum proteins are unlike those found in man. 



HUMAN 

 SERUM 



HUMAN 



SERUM 



CHIMPANZEE 

 SERUM 



BABOON 

 SERUM 



DOG 



SERUM 



RABBIT SERUM 



ANTISERUM CONTAINING 

 ANTIBODIES AGAINST 

 ^ HUMAN SERUM 



^ PLACED 



IN 

 EACH 

 TUBE 



I 



I 



J 



FIG. 6.1. Principle of the precipitin test applied to Investigation of animal 

 relationships. 



The diagram includes an additional test tube — one in which antiserum, 

 containing antibodies against human serum, is mixed with dog serum. No 

 precipitate is shown. The proteins of dog serum are so unlike those of 

 human serum that antibodies formed against the latter usually fail to react 



