FOOD. 131 



OXYGEN EEQUIRED FOR THE COMPLETE OXIDATION OF 



100 parts of starch 118.58 



"fat 287.76 



A fatty substance, therefore, has a capacity for the production of 

 carbonic acid and water, by oxidation, about 2.4 times greater than 

 that of starch. In estimating, accordingly, the requisite quantity of 

 all the non-nitrogenous matters taken together, the fat is calculated as 

 starch ; one part of fat being reckoned as 2.4 parts of starch. This 

 quantity, added to that of the carbohydrates in the food, is called the 

 " starch-equivalent " of the non-nitrogenous matters. 



But if we compare the consumption of non-nitrogenous substances, 

 on this basis, with that of albuminous matter, the latter should also be 

 reduced to its "starch-equivalent." After eliminating from albumen 

 all its nitrogen under the form of urea, its remaining constituents still 

 have a higher capacity for oxidation than a corresponding weight of 

 starch ; the exact relations of the two being as folio w^ : 



OXYGEN REQUIRED FOR THE COMPLETE OXIDATION OF 



100 parts of starch 118.58 



" " albumen 154.07 



Albumen, consequently, without its urea, has a capacity for oxidation 

 1.3 times as great as that of starch. 



When compared in this way, the albuminous matters are found to 

 constitute 22 per cent., and the non-nitrogenous matters 78 per cent, 

 of the entire food ; that is, the quantity of non-nitrogenous matter is 

 to that of albuminous matter as 3.55 to 1. 



This proportion varies to some extent with the age and condition of 

 the individual. In human milk, which at first forms the exclusive food 

 of the infant, according to the average analyses of Simon, Vernois, and 

 Becquerel, as given by Milne Edwards, the non-nitrogenous matters are 

 to the albuminous ingredients as 2.27 to 1. In cow's milk, upon which 

 the young calf is sustained, the proportion is 2.52 to 1 ; while in hay 

 and green grass, the food of the adult animal, it is 7.14 and 9.01 to 1. 

 The larger proportion of albuminous matter in the food at an early age 

 is evidently connected with the growth then taking place. As the 

 albuminous matters constitute the larger part of the solid ingredients 

 of the body, the increase in weight during the growing period demands 

 a corresponding supply of these substances in the food. 



There is also evidence that the requisite proportion of nitrogenous 

 matter varies with the amount of physical activity. A condition of 

 bare subsistence may be maintained upon a diet in which the albumin- 

 ous substances are in smaller, and the non-nitrogenous matters in larger 

 proportion ; but when the system is called upon for a greater amount 

 of muscular exertion, the proportion of albuminous matters must be 

 increased. This is well known in regard to horses and working-cattle 

 generally. In a state of comparative inactivity they may be supported 



