144 The Story of the Bacteria 



cause the biggest safeguard which the body 

 has against disease is this capacity of the 

 cells to adapt themselves, within reasonable 

 limits, to new and often adverse conditions. 

 This is combined with their habit, acquired 

 through several millions of years of inherited 

 experience, of getting back into the old ways 

 again as soon as possible. These are the 

 powers which the doctor must work with and 

 not against, with his regimen and diet, with 

 his fresh air and sunshine, with his counsel 

 and cheer, as well as with his less impor- 

 tant offerings of drugs. These body cells 

 tend to get back at their tasks again after 

 the adventures which circumstances force 

 upon them, because their ancestors, all the 

 way up the line, did so and survived, weav- 

 ing their experiences into the vitals of their 

 descendants; while collateral branches which 

 did n't do it, perished. Some folks call this 

 the principle of the survival of the fittest. 



Another of the body's most potent safe- 

 guards is its power to dispose of poisonous 

 substances, which are developed within it, 

 or get in from outside. With our food we 



