CREATION BY EVOLUTION 



in the blood of different animals will indicate the close- 

 ness of their genetic relationship, we should be able to 

 classify the whole animal kingdom by means of resemblance 

 in blood. 



The technique involved may be elucidated by a single 

 example. If we wish to find out the degree of kinship of 

 man to any kind of lower animal, we proceed as follows: 

 From a quantity of human blood we draw off only the clear, 

 colorless serum. This we inject at intervals into the veins of 

 a rabbit, for example. In time the rabbit's blood becomes 

 charged with a specific antibody for human blood and the 

 serum from the blood is known as anti-human serum. This 

 rabbit serum thus produced can now be used as a chemical 

 reagent for testing the affinities of any other blood to human 

 blood. If a few drops of it are placed in a test tube full of 

 human serum a heavy white precipitate is immediately 

 formed. If placed in the serum of a gorilla or of a chim- 

 panzee a definite precipitate is formed, but it is less abundant 

 and it forms more slowly than if human serum is used. No 

 other species tried gives so positive a reaction with anti- 

 human serum; but the baboons, the New World monkeys, 

 the marmosets, and the lemurs (all Primates) react less 

 and less readily in the order mentioned. All Primates show 

 a stronger affinity than any other mammals for human blood, 

 but if larger amounts of the reagent are used and more time 

 is allowed for the reaction, the degree of affinity between 

 man and all other mammals may be shown. Moreover, the 

 order of closeness of relationship corresponds to that already 

 worked out by the method of homology. 



Most of the larger groups of animals have been investi- 

 gated by this method and the most significant relationships 

 determined are the following: 



1. The birds show close relationship to the reptiles. 



[366] 



