CHAP. XIV.] ALIMENTATION. 173 



composition of protoplasm, so far as it has been possible to 

 analyze it, has been found to agree closely with that of the 

 fully developed organism. 



The processes of nutrition that take place in the cell are 

 essentially the same as those which take place in the fully 

 developed body. In both cases, non-living chemical substances 

 are taken in from without, and converted into material which 

 is endowed with that mysterious property we call life. 



To support life, the different food-stuffs must be taken in 

 proper proportion ; and, in order that all the tissues and fluids 

 of the body may continue in good condition and perform their 

 functions properly, they must be supplied with all the ingredi- 

 ents necessary to their constitution. A man may be starved to 

 death at last by depriving him of lime phosphate as surely, 

 though not as rapidly, as if he were deprived of albumin or fat. 

 Many a patient in less well-instructed times has been slowly 

 killed by deprivation of water, or by exclusive feeding on beef- 

 teas and jellies. 



Average composition of milk, bread, and meat. The following 

 analyses of the composition of three staple articles of diet 

 milk, bread, and meat are taken from Dalton. 



Average composition of milk in 100 parts : 



Water 86.4 



Proteids 4.3 



Sugar 5.2 



Fat 3.7 



Mineral salts 4 



Average composition of wheaten bread in 100 parts : - 



Starchy matters 56.7 



Proteids 7.0 



Fatty matters 1-3 



Mineral salts 1-0 



Water 34.0 



Average composition of beef flesh : 



Water 77.5 



Proteids 16.0 



Fat 5.0 



Mineral salts 1-5 



