RATIONAL FEEDING OF MEN 391 



digested than the same classes of nutrients in vege- 

 tables. From 93 to 95 per cent, or more of the pro- 

 teids and fats from foods of animal origin are completely 

 digested, while of vegetables not more than 85 per cent, 

 of the proteids are completely digested except in the case 

 of finely ground flour. Meats are concentrated foods as 

 they furnish large amounts of nutrients in digestible forms. 

 There is less difference in the completeness with which 

 the various meats are digested than in the ease of diges- 

 tion. Some meats, as pork, veal and mutton, which are 

 called indigestible, are slow of digestion but are quite com- 

 pletely digested. The nutrients of meats can, for all 

 practical purposes, be considered entirely digestible. 



514. Digestibility of Vegetable Foods. Vegetable 

 foods are less completely digestible than animal foods. 

 The larger the amount of cellulose or fiber, the less com- 

 pletely digested is the food. Only a very small amount 

 of the cellulose, even hydrated cellulose, of human 

 foods is available to the body. In many vegetables 

 the nutrients are enclosed in cellular tissue and 

 thus, to a certain extent, are protected from the solvent 

 action of the digestive fluids. The starches and carbo- 

 hydrates of vegetables are more completely digested than 

 the proteids. Frequently, 95 per cent, of the starch, 

 while only 80 per cent, or less of the proteids, is digested. 

 There is quite a wide range in the digestibility of the 

 nutrients of vegetable foods. The nutrients of fruits are, 

 as a rule, more completely digested than those from other 

 vegetable sources, but fruits contain only comparatively 

 small amounts of nutrients. 



