BIOMETRIC STANDARDS IN HUMAN NUTRITION 387 



ias been brought to such a stage of perfection as to measure 

 he energy transformation accompanying such slight muscular 

 ictivity as that required in the raising of the hand from the 

 ide to the mouth. The cost in calories of masticating food 

 aay be directly measured. For example, recent studies at the 

 Nutrition Laboratory by Carpenter and Benedict have shown 

 hat the muscular work in chewing gum may increase heat 

 (reduction approximately 17 per cent. The difference between 

 he heat production of a new-born infant asleep in its basket 

 ,nd crying can be precisely measured. Thus Talbot and Bene 

 dict found that the metabolism of the new-born infant is in- 

 reased on the average by 65 per cent, in crying with its attend- 

 ,nt muscular activity. Students of animal nutrition have long 

 ealized that the demands for energy of an animal standing 

 ,re far higher than that of the same beast lying down. This 

 act must be taken into account in computing the maintenance 

 lequirements of cattle and other domestic animals. 



Heat production is greatly increased after eating, and the 

 mount of the increase is closely dependent on the nature of 

 he food consumed. For example, the metabolism of a subject 

 lay be increased by 25 per cent, after a meal consisting chiefly 

 f carbohydrates, but by as much as 45 per cent, after a heavy 

 rotein meal. 



It is necessary, therefore, to eliminate all such factors in 

 etermining the standards which shall serve as bases of com- 

 arison in applied nutritional physiology. 



Since the outbreak of the war, and particularly since our 

 wn participation in the conflict, the Nutrition Laboratory has, 

 i addition to extensive investigations on the influence of sub- 

 ormal rationing upon health and efficiency, pushed forward as 

 apidly as possible its work on the establishment of nutritional 

 tandards. One phase of this program has been the statistical 

 ivestigation of the so-called basal metabolism of the human 

 idividual. 1 



Physiologists have gradually come to a general agreement 

 hat the heat production at complete muscular repose and in 

 le post-absorptive state i. e., about twelve hours after the last 

 leal shall be called the basal metabolism and shall be used as 

 standard of comparison in the investigation of all the special 

 roblems of human nutrition. 



1 The detailed measurements and the statistical constants, with full 

 iscussions of pertinent literature, are about to appear in Publication 279 

 : the Carnegie Institution of Washington. We shall not, therefore, 

 arden this brief outline with references to literature or statistical detail, 

 wo of the diagrams used here are redrawn from this publication. 



