38o HUMAN PHYSIOLOGY 



yielded. The difference between these amounts and the total 

 energy requirements of the person must be made up from 

 carbohydrates and fats. In the case of a working-man 

 requiring 3500 Calories, and consuming 100 grms. of proteid 

 per diem, this leaves about 3000 Calories to be supplied by 

 fats and carbohydrates. 



In determining the proportionate amounts of these, two 

 factors have to be considered first, the relative cost, and, 

 second, the limitation of the power of digestion of each. 



Carbohydrates are enormously cheaper than fats as a 

 source of energy. Margarine at 8d. per Ib. will yield 435 

 Calories for a penny, while sugar at 2|d. per Ib. will yield 

 1860 Calories for the same sum. But the use of carbo- 

 hydrates as a source of energy is limited by the fact that in 

 most individuals digestive disturbances are apt to supervene 

 if more than from 500 to 600 grms. are consumed. 



A diet should therefore not contain much more than 500 

 grms. of carbohydrates, and these will yield 2050 Calories of 

 energy. 



This leaves about 950 Calories to be supplied by fats, an 

 amount which is nearly met by 100 grms. of fat yielding 930 

 Calories of energy. This quantity of fat most people can 

 easily digest. 



A typical diet for an average man doing moderate muscular 

 work would thus be 



Amount. Energy Value in 



Calories. 



Proteids ... 120 410 



Carbohydrates . . 500 2050 



Fats 100 930 



3390 



or very nearly the 3500 Calories. 



A reference to Atwater's table gives the dietary require- 

 ments of a woman or of a child of any age, and thus renders 

 it easy to make out the diet of a family or public institution. 



IY. The Diet must be capable of Digestion, Absorption, 

 and Assimilation. While proteids, carbohydrates, and fats 

 in the alimentary canal undergo the changes already de- 



