THE ORIGIN OF MAN 



tive sera can be produced in this fashion. 1 This 

 fact clearly points to a profound resemblance in 

 the bodily chemistry a physiological similarity 

 no less striking than the anatomical resemblances 

 so familiar of man and these creatures. 



The second recent discovery points in the same 

 direction. It has lately been shown that the blood 

 of each species of animal differs radically from 

 that of every other. Hitherto it has hardly been 

 possible for the expert, summoned to give evidence 

 in a trial for murder, let us say, to decide whether 

 or not specimens of blood submitted to him are 

 human or not. Mammalian blood could be dis- 

 tinguished from, say, the blood of birds, by means 

 of the characteristic shape of the blood-corpuscles 

 which is common to all mammals save the camel; 

 but to distinguish between the blood of a man and 

 a dog was often impossible. Now, however, it has 

 been shown that when the blood of a given animal, 

 say a dog, is injected into the blood-vessels of an 

 animal of another kind, such as a cat, the red 

 corpuscles of the cat are destroyed and disinte- 

 grated ; whereas if the dog's blood be injected into 

 another dog no such disintegration occurs. Hence, 

 in distinguishing between the blood of a man and 

 a dog it is only necessary to make a sterile solution 



1 The close relation of man to the anthropoid apes has lately 

 raised in remarkable degree the market-price of these creat- 

 ures. Every living specimen that reaches Europe is bid for, 

 by letter and cable and telegram, by workers at medical prob- 

 lems in Paris, London, and Berlin. 

 137 



