ANIMAL NUTRITION. 67 



a reserve of force. Fat has a greater value as a heat and 

 force producer than any other ingredient of food. 



The carbo-hydrates of the food include starch, sugar, 

 and cellulose ; these substances consist of carbon, hydrogen, 

 and oxygen, the last two elements being in the proportion 

 to form water — hence the name. Various other non-nitro- 

 genous constituents of food, as pectin, lignose, and vege- 

 table acids, are also generally included under this title, 

 though not strictly speaking carbo-hydrates. Carbo- 

 hydrates form the largest part of all vegetable foods. 

 They are not permanently stored up in the animal body, 

 but serve, when burnt in the system, for the production of 

 heat and mechanical work. They are also capable, when 

 consumed in excess of immediate requirements, of con- 

 version into fat. 



Carbo-hydrates are of less value, for the same w^eight 

 consumed, than either albuminoids or fat. Frankland 

 found that 100 parts of fat when burnt gave the same 

 amount of heat and force as 211 parts of albumin (urea 

 deducted), or 232 parts of starch. It is commonly reckoned 

 that 1 part of fat is equivalent to 2*44 parts of starch. 

 Cane sugar, according to the Rothamsted experiments with 

 pigs, has the same feeding value as starch. Cellidose, 

 being more difficult of digestion, has probably a smaller 

 value than either. 



The amides, carbo-hydrates, and fat, are quite incapable 

 of adding to the nitrogenous tissues of the body. They 

 may, however, have this effect indirectly by protecting the 

 albuminoids of the food from oxidation. A moderate 

 quantity of albuminoids supplied to a growing animal will 

 thus produce a larger increase of muscle when accom- 

 panied by a supply of carbo-hydrates or fat than if con- 



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