108 THE CHEMISTRY OF THE FARM. 



duction of heat and mechanical work is the principal 

 result which food accomplishes in the animal body ; the 

 capacity for producing heat is also intimately related to 

 the capacity for producing fat. On the other hand, the 

 amount of heat which any food is capable of producing 

 stands in no relation to its power of increasing or renew- 

 ing the nitrogenous tissues of the body. We may, how- 

 ever, safely assert that the amount of heat generated by 

 the combustion of the digestible constituents of any food 

 will be a fair guide to its nutritive value, when the diet 

 of which it forms a part supplies a sufficient amount of 

 digestible albuminoids, and this will be the case whenever 

 foods are skilfully employed. 



According to recent determinations of the heat- pro- 

 ducing power of the various food constituents, their com- 

 parative values in this respect are : 



Fat 229 



Albumin . ... . . .107 



Starch 100 



Cane Sugar and Gum .... 97 



Glucose and Milk Sugai- .... 90 



Cellulose (about) 86 



Asparagine 49 



The albumin and asparagine are here reckoned as 

 minus the nitrogenous matter (urea) excreted by the 

 kidneys. 



If we take the quantities of digestible fat, albu- 

 minoids, amides, carbo-hydrates, and cellulose, supplied 

 by any food, and multiply them by their respective heat 

 coefficients, the sum of the products will represent the 

 heat-producing capacity of the food when consumed 



