CHAPTER XIV 



SAFEGUARDS OF THE BODY AGAINST DISEASE 



WHEN we try to learn more about the 

 human body than we can by ob- 

 serving its form and structure and the various 

 obvious things which it can do, we are led 

 back to the time when that mysterious potency 

 called life stole in upon the earth in the pri- 

 meval silences. And we are obliged to trace 

 the changes which, through stress of circum- 

 stance, have slowly shaped, out of a single 

 cell, the various cell communities and their 

 marvellous correlated activities which make 

 the human being of to-day. 



All these changes have been brought about 

 by the adaptation of form and activity to new 

 environments. And we can discern here and 



there through all the various cells and organs, 



141 



