126 FOOD. 



Here the oxygen is present in much diminished proportion ; and, for 

 complete oxidation of the fat, to form carbonic acid and water, the 75.93 

 parts of carbon will require 202.48 parts of oxygen, and the 12.15 parts 

 of hydrogen will need 85.28 additional, over and above the 11.92 parts 

 of oxygen already present. Thus the quantities of oxygen appropriated 

 during complete oxidation, by starch and fat respectively, are as 

 follows : 



QUANTITY OP OXYGEN REQUIRED 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 car- 

 bonic 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 upon 

 this basis ; one part of fat, by weight, being reckoned as equal to 2.4 

 parts of starch. This quantity, added to that of the carbohydrates in 

 the food, is sometimes called the " starch-equivalent" of the non-nitro- 

 genous matters. 



If we ascertain the amount of solid albuminous and non-nitrogenous 

 matter contained in the daily food of an ordinary nutritious diet of 

 mixed quality, we find that the non-nitrogenous matters, reckoned as 

 starch, amount to four or five times as much as the albuminous ingredi- 

 ents. A comparison of our own observations with the estimates and 

 diet tables of Moleschott, Payen, and Playfair, all of which correspond in 

 the main with each other, gives the following as the average daily 

 quantity of these two classes of proximate principles in the food. 



Albuminous matter ...... 130 grammes. 



Non-nitrogenous matter, as starch .... 600 " 



Thus albuminous matter constitutes rather less than one-fifth of the 

 entire food, for a healthy adult in active occupation ; and its quantity 

 is to that of the non-nitrogenous matters as 1 to 4.62. 



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 young infant, according to the average analyses of Simon, Yernois, 

 and Becquerel, as given by Milne Edwards, the albuminous ingredients 

 are to the non-nitrogenous matters reckoned as carbohydrates in the 

 proportion of 1 to 2.95. In cow's milk, upon which the young calf is 

 sustained, the proportion is as 1 to 3.27 ; while in green grass and hay, 

 upon which the adult animal feeds, it is as 1 to 11.70 and 1 to 9.28 re- 

 spectively. The larger proportion of albuminous matter in the food at 

 this early age is evidently connected with the growth which is then 

 taking place. As the nitrogenous principles constitute much the larger 

 part of the solid organic matters contained in the body, the steady in- 

 crease 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 



