134 THE CONTROL OF LIFE 



of food, sufficient rest, and adequate removal of waste- 

 products. 



§3. The Nervous System 



As Sir Michael Foster said, there are two master- 

 activities in the body, and all the rest are ancillary or 

 sustentative. One of the master-activities we have 

 already dealt with very briejfly — the contractility resident 

 in the muscular system. The other master-activity 

 is the irritability resident in the nervous system. This 

 implies feeling and controlling, in its higher reaches, 

 thinking and purposing. It is the nervous system — 

 especially the brain — that starts, regulates, and controls 

 the motor apparatus represented by the muscles. In 

 some ways the nervous system is like a storage-battery, 

 contributing the initial spark that sets the combustion 

 a-going. In other ways it is the intermediary between 

 the rest of the engine and the outer world, so that suit- 

 able responses are made to what happens outside. It 

 is also the intermediary between the various parts of 

 the body, so that they work into one another's hands 

 harmoniously. The learned word for this function is 

 integrative — ^making many members a whole (see C. S. 

 Sherrington's Integrative Action of the Nervous System). 



An understanding of the general nature of the nervous 

 system is indispensable if we are to understand health 

 even a little bit ; so we must linger over some funda- 

 mental facts. 



{A) Our nervous system consists of (1) the brain — 

 a world in itself with many nerve-centres integrated 



