OUK NATURAL INHERITANCE 51 



differences in the minute details of the brain ; there are 

 differences in the rate at which the brain works, and 

 so on ; but, barring accidents, there are no differences 

 in the general architecture of the brain. And so for 

 other parts. Thus we may picture in every human 

 inheritance a sort of fundamental organisation which 

 has ceased to show more than detailed variations. 



Along with the common stock of human organisation 

 there is, of course, a common stock of human capacities. 

 The two aspects of form and function, structure and 

 activity, are inseparable. Just as all ordinary mammals 

 have a capacity for being ' warm-blooded ' (i.e. regulat- 

 ing production and loss of heat so that an approximately 

 constant temperature is sustained), and a capacity for 

 profiting by experience, so all normal human beings 

 have a capacity for speech and a considerable capacity 

 for intelligent inference. The Zulu, a fine physical 

 type, is alert, quick to put two and two together, shrewd 

 within the limits of his knowledge and interest, but not 

 much given to poetry or philosophy. Experiments in 

 education have shown, however, that in the Zulu, and 

 in similar cases, the imaginative and reflective capacities 

 are there all right. One may say that the power of 

 intelligent inference is a universal human character, 

 part of the common stock of heritable qualities, though 

 it varies greatly in its expression according to educational 

 opportunities, according to the general pitch of the life 

 and according to diversity in the more superficial and 

 variable elements in cerebral endowment. The same 



