SECTION III: CELL COMMUNITIES 



CHAPTER XIII 



THE ARMY WHEREWITH THE BODY WAGES WAR 

 WITH NATURE THE MUSCLE CELLS 



" Tho' born to fight, 

 Yet, mix'd and soften'd, in his work unite ; " 



POPE. 



IN the animal body there are various kinds of cell communities. 

 There seems to be no doubt that originally each cell was self- 

 supporting, and a small cell-community, like a small village in a 

 remote corner of civilisation, was able to perform all necessary 

 activities without the help of other communities. In a big 

 complex concern like the mammalian body, however, each cell 

 community has specialised in some form of activity, and it has 

 therefore to depend on other communities for certain necessities. 

 No such cell is absolutely self-supporting. For the same reason 

 we cannot validly consider any cell as typical of all others. Each 

 has its own particular duty to perform and is adapted to perform 

 that particular duty most economically. It could, if circum- 

 stances compelling it arose, do other things usually left to other 

 cells, but would perform these unaccustomed duties clumsily and 

 uneconomically. 



The dominant cell communities in the somatic body are those 

 forming the muscles. Their activity, to a great extent, regulates 

 all other changes taking place in the body. They demand for 

 their use the lion's share of the energy intake of the body. The 

 bulk of the repair material in the food is earmarked for their use. 

 They keep a firm hand on the transport system and soon cause a 

 " speeding up " if supplies fall short of their needs, or if the bye- 

 products of their activity are not removed with sufficient rapidity. 

 The system of inter-communication between cell-communities 



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