THE FOOD AND DIGESTION 379 



Recently Chittenden has recorded a prolonged series of 

 investigations upon this question by which he shows that in 

 five professional men for periods of from seven to nine 

 months, in eight student athletes for from four to seven 

 months, and in thirteen soldiers for five months, a nitro- 

 genous equilibrium and perfect physical and mental health 

 could be maintained with an intake of from 35 to 56 grms. 

 of proteid per diern. 



The work done by these individuals is not recorded, but 

 from the daily routine of the soldiers, whose chief work 

 appears to have been two hours' exercise in a gymnasium, it 

 must be classed as very moderate. The fact that the energy 

 value of the diets in the case of the soldiers was only 2500 to 

 2800 Calories seems either to confirm the opinion that they 

 were not called upon to do severe work or to suggest that our 

 present estimates of the loss of energy as heat from the body 

 (p. 378) are erroneous. 



While these results certainly prove that men can maintain 

 health and muscular efficiency for long periods on about half 

 the amount of proteid which is usually consumed, they do 

 not demonstrate that, in the case of those subjected to 

 strenuous and sustained muscular work, such a reduction is 

 desirable, nor do they indicate that in growing children a 

 reduction in the amount of proteids usually consumed may 

 be safely allowed. A study of a very large series of dietaries 

 of different races shows that, unless absolutely prevented by 

 poverty, the average man consumes over 100 grms. of pro- 

 teid per diem, and that those in muscular training tend to 

 consume very much larger amounts. Bearing in mind the 

 importance of proteids as muscle builders, it is safe to con- 

 clude that about 120 grms. of proteids should be allowed per 

 man per diem, at least in the labouring classes. 



Ill; Part played by Carbohydrates and Fats. The carbo- 

 hydrates and fats have to supply the energy not supplied by 

 the proteids. The amounts which must be consumed will 

 thus depend, first, on the amount of proteid taken, and, 

 second, on the energy requirement of the individual. If 100 

 grms. of proteid are taken, this will yield 410 Calories of 

 energy, while if only 50 are consumed, 205 Calories will be 



