THE CONTROL OF LIFE 91 



with large numbers of molecules) their 

 average behavior can be predicted in 

 certain respects with surprising accuracy. 

 This sort of prediction depends on the 

 use of statistical methods which are be- 

 coming very useful in biology. 



Let us now turn to another subject 

 which is destined to play a prominent 

 role in biological progress, namely, the 

 control of life-processes. 



We have already learned to control 

 the development and behavior of organ- 

 isms to such a remarkable degree that it 

 would be difficult to set any limit to what 

 we may hope to accomplish. 



Every one is aware, for example, of the 

 way in which the development of the 

 human body is controlled by the thyroid 

 gland. If it fails to function properly the 

 individual may develop into a cretin, 

 that is, a dwarf with a peculiar cast of 

 countenance, a dry and parchment-like 

 skin, defective in mind or even idiotic. 

 Transplantation of a thyroid gland into 

 various parts of the body in childhood 



