126 THE CONTROL OF LIFE 



summed up by saying that Man's instincts are very 

 generalised and that his restless intelligence prompts 

 him to experiment with himself and to ' chance things.' 

 He has very little of a resting' instinct ; he has 

 relatively little clear awareness of what is good for 

 him ; he does not understand the significance of pain 

 and sleeplessness as danger-signals ; he is so safe in his 

 stronghold of wits that he runs risks for the sake of 

 immediate pleasure. In a way quite unique among 

 organisms he uses artificial means to stimulate his 

 energies or to dull the sense of fatigue, and however 

 useful or pleasant these means may be, no one can 

 pretend that they do not involve some risk. By 

 ambition, zeal, or dire necessity, man is often forced to 

 overwork himself, and then he often seeks " the shortest 

 way out," for alcoholism is often the nemesis of an 

 attempt to evade occupational fatigue. In the very 

 imperfectly organised social systems of to-day it is 

 often difficult for an ordinary citizen to secure a mode 

 of life that allows enough open air, exercise, and 

 change. And so Man falls from the norm of health. 



§2. The Body as Engine 

 An animal is much more than an engine, for it ig 

 self -stoking, self-regulating, self-adjusting, self-repair- 

 ing ; it can register experiences and profit by them ; 

 it is more or less aware of what it is doing, and often 

 plans and purposes ; it can give rise or help to give rise 

 to other creatures like itself. We have elsewhere {The 

 System of Animate Nature, Gifford Lectures, 1920) tried 



