CHAPTER VII 



THE ADJUSTMENT OK, COORDINATION OF THE 

 WORK OF ORGANS AND CELLS 



A great physiologist once said, " Science is not a body of 

 facts ; it is the explanation of facts." Some of the most im- 

 portant chapters of science are those which seek to explain 

 facts so well known and obvious that we are apt to forget 

 that they need explanation. When anything irritates the 

 lining of the nasal cavity we sneeze ; when it irritates the 

 larynx we cough; when it irritates the exposed surface of 

 the eyeball we wink. These three facts are well enough 

 known ; but it is safe to say that anyone considering the 

 matter for the first time would find it difficult to explain 

 how it comes about that anything going " down the wrong 

 way " does not make us sneeze or wink, but sets us to 

 coughing. The answer to the general question thus raised 

 is the subject of this chapter, which considers the adjust- 

 ment of the work of the individual cells and organs of the 

 body, each to do its work at the proper time and so to play 

 its due part in the work of the organism as a whole. 



The more we think of it, the more wonderful does this 

 fact of adjustment appear. The millions of living cells are 

 in a way individual units, and communities of individuals do 

 not invariably work together. Let us compare the human 

 body in this respect with bodies or groups of men or boys. 

 In a game of football each team is a body of eleven indi- 

 viduals, and each individual is assigned to a definite posi- 

 tion to do definite things as occasion arises. Theoretically, 

 under given conditions of the game it is the work, or 

 function, of the " left tackle " to prevent a certain player 



