332 VETERINARY PHYSIOLOGY 



under the influence of yeast. In cold neutral or acid solutions 

 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 laevulose. 



Glyeogen is animal starch. It gives an opalescent solution 

 and strikes a brown colour with iodine. 



Cellulose, which forms the capsule of vegetable cells, also 

 belongs to the group of polysaccharids. It is characterised by 

 its insolubility and by the fact that it is not acted upon by the 

 starch digesting enzymes of the alimentary canal. 



The energy value of the carbohydrates is about the same 

 as that of the proteins. 



Energy Value of the Proximate Principles of the Food. 

 1 gramme of 



Protein 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 (Chemical Physiology). The white colour of milk 

 is due to its being a fine emulsion of fat globules floating in 

 a clear plasma. Hence, when the cream is removed, milk 

 becomes less white and less opaque. Its specific gravity is 



