184 THE PROBLEM OF EVOLUTION 



ment is falsified. The absolute cranial capacity 

 does not tell us whether the owner of the skull 

 had a large or a small brain in proportion to 

 his size. 



According to Dr. Plotz, increased cerebral activity 

 tends to adapt man to his surroundings, and also 

 his surroundings to him, much better than the 

 greater development of the extremities that he once 

 possessed; therefore the consideration of the form 

 of the body is not so important as the consideration 

 of the cerebral capacity, because from this we can 

 trace the degree of increase in the size of the brain 

 that filled the cranial cavity. As the organisation 

 of the brain advanced, the intelligence of man 

 developed. 



There is an element of truth in these asser- 

 tions, for the difference in the formation of the 

 brain is the chief distinguishing mark between 

 man and beast, as far as their bodies are 

 concerned. I discussed this point in more 

 detail in my third lecture (p. 56, etc.). But as 

 the development of the human brain is more 

 perfect than that of the highest apes, because 

 the human brain is the instrument of intel- 

 lectual activity, I added the remark that all 

 the bodily differences between man and beast 

 are ultimately a result, a function, of their 

 mental difference. 



Dr. Plotz makes a mistake, however, in 



