3 i8 HUMAN PHYSIOLOGY 



tions most of them strike a blue or brown colour with iodine. 

 By boiling with a mineral acid and by the influence of various 

 ferments they break down, take up water, and become mono- 

 saccharids the starches yielding the dextroses, and inulins 

 yielding Isevulose. 



Glycogen is animal starch. It gives an opalescent solution 

 and strikes a brown with iodine. 



The energy value of the carbohydrates is about the same 

 as that of the proteids. 



Energy Yalue of the Proximate Principles of the Food. 

 1 gramme of 



Proteid yields . . . .4-1 Calories. 

 Carbohydrate yields . . .4-1 

 Fat yields .... 9-3 



The Sources of the Various Proximate Principles of 

 the Food. 



The proximate principles are in part derived from the 

 animal, in part from the vegetable kingdoms. While some 

 races procure their food entirely, or almost entirely, from the 

 former, others depend almost entirely on the latter. The 

 vast majority of mankind, however, use a mixture of animal 

 and vegetable foods. 



Animal foods may be classified as 



1. Milk and its Products, Cream, Butter, and Cheese. 



2. Flesh. 



3. Eggs. 



1. Milk. The characters of human milk are considered at 

 p. 411. Cow's milk is an important constituent of the diet. 

 Its average composition compared with human milk is as 

 follows : 



