36 THE WHENCE AND THE WHITHER OF MAN 



tide of protoplasm requires food and oxygen, and pro- 

 duces waste. The particles of protoplasm in our new, 

 larger amoeba can therefore receive only half as much 

 oxygen as before, and rid themselves of their waste 

 only half as fast. There is danger of what in our 

 bodies would be called suffocation and blood-poisoning. 

 The amoeba having attained a certain size meets this 

 emergency by dividing into two small individuals, the 

 division is a physical adaptation. But the many-celled 

 animal cannot do this ; it must keep its cells together. 

 It gains the additional surface by folding and plaiting. 

 And the complicated internal structure of higher ani- 

 mals is in its last analysis such a folding and plaiting 

 in order to maintain the proper ratio between the ex- 

 posed surface of the cells and their mass. And each 

 cell in our bodies lives in one sense its own individ- 

 ual life, only bathed in the lymph and receiving from 

 it its food and oxygen instead of taking it from the 

 water. 



But in another sense the cells of our body live an 

 entirely different life, for they form a community. 

 Division of labor has taken place between them, they 

 are interdependent, correlated with one another, subject 

 therefore to the laws of the whole community or organ- 

 ism. There are many respects in which it is impos- 

 sible to compare Robinson Crusoe with a workman in 

 a huge watch factory ; yet they are both men. 



Both the amoeba and we live in the closest relation 

 to our environment, and conformity to it is evidently 

 necessary : life has been denned as the adjustment of 

 internal relations to external conditions. We contin- 

 ually take food, use it for energy and growth, and return 

 the simpler waste compounds. We are all of us, as 



