FUNCTIONS OF NUTRIENTS 35 



take the average figure that fat is 2-3 times as valuable 

 as carbohydrates for this purpose. 



Fat, like carbohydrates, supplies "energy," or the 

 power of doing muscular work to the animal ; either 

 internal, in digesting foods, maintaining the circulation 

 of blood, etc. ; or external, for pulling loads, etc. This 

 can be proved by limiting the albuminoids and carbo- 

 hydrates in the ration and increasing the fat ; the 

 animal is then able to do more work after the addition 

 of fat has been made. 



The fat of food may also be stored as "fat" in the 

 animal body, although the composition of the body 

 fat as well as the fat in milk becomes slightly changed 

 in composition and properties from the fat of food. 

 This is not so difficult to understand, seeing the fat is 

 broken down in the body during digestion, 1 and 

 immediately after absorption built up again into animal 

 fats. 



Albuminoids. The albuminoids are the only food 

 constituents that have the power of forming lean meat 

 in the animal body, hence they are called "flesh- 

 formers." They may also form the ligaments, tendons, 



1 A few years ago fat was considered to be absorbed into the 

 blood without change, but this theory could not explain why 

 it was that the fats of the animal body and in milk differed 

 considerably in properties and composition from the fats of the 

 food. The modern and more rational view is that the fats are 

 split up by the digestive juices into fatty acids and glycerine. 

 These fatty acids unite with the alkaline salts in the bile to form 

 soluble soaps. The glycerine and soluble soaps are then absorbed 

 into the circulation in the small intestines, and shortly after are 

 reunited into animal fats, provided they are in excess of the 

 requirements in the body for heat and force. If not, the carbon 

 is oxidised with the oxygen in the blood to carbon dioxide (CO 2 ), 

 and becomes a source of heat and energy. 



