THE ABSORPTION AND USE OF FOODS 505 



One consideration that has been suggested as probably significant 

 is that the low protein diet, although adequate for immediate 

 maintenance, does not afford the Body sufficient reserve vitality 

 to place it in the best situation for resisting infections or other 

 debilitating influences. Emphasis has also been placed on the 

 fact that the poorer inhabitants of Bengal, who live of necessity 

 on a low-protein diet, are deficient both in strength and endurance. 

 Conservative students of the subject are inclined to the opinion 

 that our present dietary habits, based as they are upon centuries 

 of experience, are probably in the long run better suited to our 

 needs than radically altered dietaries, which may be theoretically 

 sound, but lack the confirmation of long experience. 



The allowance of protein in standard diets varies from 80-90 

 grams daily, which is the average amount consumed by American 

 College students, to the 115-120 grams considered by some Euro- 

 pean dietitians suitable for the European laborer. In contrast 

 with these figures are the allowances of 40-60 grams proposed 

 by the advocates of a low-protein diet. While we may properly 

 adopt a conservative attitude with reference to the low-protein 

 controversy, we are not thereby justified in going to the opposite 

 extreme. Excessive consumption of meat, particularly by people 

 who lead sedentary lives, undoubtedly is attended by various 

 evils, although most of these are referable to other causes than over- 

 consumption of proteins. 



The Liberation of Energy in the Body. We have seen that all 

 the energy liberated by the Body can be expressed in terms of 

 heat-units, but it is not to be concluded, therefore, that heat energy 

 is the only form manifested by the Body. As a matter of fact the 

 Body undoubtedly converts the potential energy of the food into 

 at least three forms of kinetic energy; chemical, the carrying on of 

 the digestive and other chemical processes of the Body; mechanical, 

 the working of the skeletal muscles, as well as of the heart, the 

 muscles of respiration, and the muscles of the viscera; and thermal, 

 the direct production of heat by oxidation processes. This latter 

 form of energy, although far exceeding in amount both the others 

 together, may be looked upon as in large degree a by-product of 

 the mechanical work of the Body, and arising through the ineffi- 

 ciency of the body machinery. We know that most of the heat of 

 the Body is produced in the muscles, and that though these are 



