CREATION BY EVOLUTION
in the blood of different animals will indicate the closeness 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 chimpanzee 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 from 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 investigated by this method and the most significant relationships determined are the following:
1. The birds show close relationship to the reptiles.
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