82 THE CHEMISTRY OF THE FARM. 



the albumin oxidised.* When the albuminoids, either of 

 the food or of the wasting tissues, are only partially 

 oxidised, fat as well as urea may be produced. According 

 to the new determinations of the heat evolved on combus- 

 tion, 100 parts of albumin must yield less than 47 parts 

 of fat. 



The amides consumed as food are burnt in the system, 

 and their nitrogen excreted as urea. Amide? cannot 

 supply the place of albuminoids as muscle-formers, but by 

 combustion they serve for the production of heat and force. 



The fats contained in food are similar to those found 

 in the animal body, but an animal is apparently capable 

 of transforming one kind of fat into another. The fat 

 of the food is either burnt in the animal system to furnish 

 heat and mechanical energy, or it is stored up as reserve 

 matter. Fat has a greater value as a heat and force 

 producer than any other ingredient of food. 



The carbo-hydrates of the food are chiefly 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-nitrogenous constituents of food, as pectin, 

 lignin, and vegetable 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 cf heat and mechanical work. They 

 are also capable, when consumed in excess of immediate 

 requirements, of conversion into fat. 



* There are small quantities of other nitrogenous products, as uric 

 and (in the case of herbivorous animals) hippuric acid, voided in the 

 urine, but they do not in this place require our attention. 



