THE. DESCENT OF MAN 69 



blood-reaction points to a close relation between 

 creatures that are morphologically far apart. It 

 would seem that we cannot make much use of evi- 

 dence derived from similarity of blood, if compara- 

 tive morphology arrives at contradictory results. 



Moreover, recent investigations by Uhlenhuth 

 and Friedenthal tend to throw doubt upon the 

 actual existence of the alleged similarity between 

 human blood and that of the higher apes, and this 

 circumstance renders untenable all the conclusions 

 based upon this similarity, viz. that man is very 

 closely related to the higher apes, or is even an ape 

 himself. I should like to refer to some recent 

 microscopical investigations made by Raehlmann 

 into the red corpuscles. Those occurring in human 

 blood present certain peculiarities that are not 

 found in the blood of other vertebrates. In the 

 course of his researches into the causes of sleeping- 

 sickness, Brumpt found that, as a rule, the disease 

 followed when other mammals were inoculated 

 with the blood of sufferers from sleeping-sickness ; 

 a few apes and pigs alone were exempt. 1 



This is a very remarkable fact. Are we to infer 

 from it that the composition of human blood differs 

 most completely from that of the blood of some 

 apes and pigs ? Such an inference would mani- 

 festly be false; but this fact shows us how care- 

 fully we ought to proceed in drawing conclusions 



1 Of. Modern Biology, p. 469. Notes of further research will be found 

 in La Nature, November 17, 1906, pp. 390-392. 



