70 ORGANIC EVOLUTION 



measurable psychological differences between man 

 and his nearest relatives. Here I have been con- 

 cerned merely with the comparative anatomy of 

 the brain. We shall see that the psychological 

 differences are much more marked than the 

 anatomical, but we shall completely fail to discover 

 the reasons of this apparent disparity between com- 

 parative function and comparative structure. 



In considering the relationships of the human 

 body — relationships which are of such profound in- 

 terest when regarded as facts from which its origin 

 may be inferred — the contemporary writer upon 

 organic evolution is able to avail himself of certain 

 •recently discovered facts which were entirely un- 

 known to the founders of this theory : facts some 

 of which are no less than bizarre. 



In order to justify my use of this word, I will 

 begin with the most striking and the most recently 

 discovered of these facts. It is of immediate 

 interest alike to the juryman and the biologist. 



It occasionally becomes a matter of medico-legal 

 importance to determine whether a suspicious blood- 

 stain on a garment or a weapon is of human origin. 

 This determination offers serious difficulties even to 

 the expert. In the case of fresh blood if is possible 

 to isolate a few of the red corpfu^cles on a minutely 

 graduated stage, and, by' examining them with a 

 rather high power of the microscope, to determine 

 their "size. Their shape is identical 1 in all the 

 mammalia, with the single exception of the camel, 

 but their size varies within small limits in different 



1 They are biconcave circular discs. 



