80 ORGANIC EVOLUTION 



not. But if we consider the whole series of diseases 

 which are apparently peculiar to man, and proceed 

 to make upon the lower animals experiments with 

 their microbes — or in cases where the microbe has 

 not been isolated, with infective material derived 

 from a case of the disease — we find that a number x 

 of the diseases thought to be peculiar to man are 

 communicable to the anthropoid ape. If, now, we 

 make further experiment with other animals, and 

 especially with the lower apes, Ave find that there is 

 a whole series of diseases which are communicable to man 

 and the anthropoid apes but to no other animal. 



If it is permitted to draw any inference from this 

 fact — and, indeed, science does not ask any one's 

 permission to think nowadays — we must regard it 

 as a proof of blood-relationship between man and 

 the anthropoid ape only one degree less striking 

 than the instance furnished us by comparative 

 hsematology. 2 



Just as we found the surgeon practising on the 

 anthropoid ape so as to enable him dexterously 

 to operate on man, so we now find that medicine, 

 also, is devoting great attention to the anthropoid 

 ape as a subject for experiment. Already sub- 

 stantial results have accrued, to the immediate 

 benefit of humanity, from the recognition of the 

 fact that for purposes of practical medicine it comes 

 almost to the same thing whether an experiment is 

 performed — as most people agree is justifiable — 

 upon the chimpanzee or — as most people think 



1 This work is in its infancy. It remains to be seen how com- 

 prehensive these statements may ultimately become. 



2 The study of the blood is nowadays so important that, if the 

 word conchology is justified, so, surely, is haematology. 



