FOOD. 127 



principles varies in the adult with the amount of physical activity. A 

 condition of bare subsistence may be maintained upon a diet in which 

 the albuminous substances are in smaller, and the non-nitrogenous 

 matters in larger proportion ; but when the system is habitually called 

 upon for a greater amount of muscular exertion, the proportion of 

 albuminous matters in the food must be increased. This is a well-known 

 fact in regard to horses and working cattle generally. In a state of 

 comparative inactivity they may be supported mainly upon grass or 

 hay, in which the proportion of nitrogenous to non-nitrogenous matter 

 is not more than 1 to 9.28 ; but when employed in active labor they 

 require a liberal supply of oats, in which the proportion is as 1 to 1.13. 

 In Dr. Play fair's diet tables, which were collected with great care from 

 a variety of sources, including those of prisons and infirmaries, those of 

 the American and European armies during peace and in active service, 

 and of certain hard-working laborers, the increase of albuminous matter 

 with increased labor is a marked feature. While in a bare subsistence 

 diet the proportion of albuminous to non-nitrogenous matter is as 1 to 

 5.87, in that of active laborers it is as 1 to 4.34. The following table 

 will show the relative increase of the two kinds of food under different 

 conditions of exercise, as calculated from Dr. Play fair's data. 



KELATIVE INCREASE, UNDER DIFFERENT CONDITIONS, OF ALBUMINOUS AND NON- 

 NITROGENOUS MATTERS IN THE FOOD. 



Albuminous Non-nitrogenous 

 matter. matter. 



Bare subsistence diet . . . .100 100 



Full diet with moderate exercise . . 180 161 



Diet of active laborer .... 232 171 



Diet of hard-worked laborer . . .242 189 



As these diet tables were adopted by the various civil and military 

 authorities as the result of long experience in the practical adaptation 

 of food to the amount of work performed, they may be regarded as 

 expressing with great approximation to certainty the physiological re- 

 quirements under different conditions. They are corroborated by the 

 variation in diet adopted in the convict establishments of Great Britain, 

 as given by Pavy. 1 In the change from " Light-labor Diet" to " Hard- 

 labor Diet," while the non-nitrogenous food is increased only 13.37 per 

 cent., the albuminous food is increased 16.15 per cent. 



It is evident, therefore, that increased physical exertion requires a 

 greater proportional increase in the albuminous than in the non-nitro- 

 genous ingredients of the food. 



It is also a matter of interest to determine the quantity, source, and 

 destination of the different chemical elements entering into the composi- 

 tion of the food. Taking the average chemical composition of albumin- 

 ous matters and fat, and that of the carbohydrates, we find that a man 

 under ordinary full diet takes into his system daily the constituents of 

 the food, in round numbers, as follows : 



1 On Food and Dietetics. Philadelphia edition, 1874, p. 433. 



