SUMMARY 213 



What has been said above regarding nutrition may be 

 thus summarised : — 



1. Food is required for two purposes — maintenance and 

 growth. There is some evidence that certain substances 

 are necessary for the latter and not for the former. 



2. The adequacy of a diet has a quantitative and a 

 quahtative aspect. Quantitatively, an adequate supply of 

 calories is required to provide energy for the hfe-processes. 

 For this purpose proteins, fats and carbohydrates are to 

 a great extent mutually replaceable. But besides the 

 calorie supply there is need for certain substances which 

 cannot be made by the animal body. Some of these are 

 amino-acids. Others are bodies of unknown composition, 

 called vitamines. These substances are necessary not as 

 energy providers but as contributing some essential part of 

 the cell-machine. 



