290 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 



ment ; in other words, the caloric requirement had been lowered nearly 

 one-half. Using the level of 3,100 calories actually found with Squad 

 A from October 1 to 4, we see that the dietetic restrictions have lowered 

 the caloric requirement 1,150 calories, or a little more than one- third. 

 Even if we raise slightly the caloric requirement at the lower level of 

 body-weight, we would still have reduced the normal requirement of 

 3,100 calories not less than one-third. It must again be pointed out, 

 however, that body-weight is a very uncertain criterion of the condi- 

 tion of the body reserves. A period of two weeks is too short to obtain 

 results of definite significance. In this particular case, however, with 

 the majority of our subjects two periods separated by nearly a month 

 or six weeks indicated approximately the same uniformity of weight- 

 level with the same caloric intake ; hence, we believe we are more justified 

 in using these short periods of constancy in body-weight as a measure 

 of maintenance than if we had but one period. The general con- 

 clusion can be drawn, therefore, that using the constancy in body- 

 weight at the lower level as a criterion, the food requirements are 

 approximately one-third less than they are at the higher level. 



DIGESTION EXPERIMENTS. 



Normal, healthy man, subsisting upon modern well-prepared and 

 well-cooked food materials, exhibits a uniformity of digestive pro- 

 cesses that is, in a sense, rather remarkable. The so-called '' digesti- 

 bility' ' of our modern food materials can be predicted from standard 

 figures with great accuracy. Hence a digestion experiment as such, 

 particularly when ordinary food materials are used, is hardly justifiable. 

 On the other hand, with a great restriction in diet, the evidence is not 

 sufficiently extensive to show whether or not there would be a dis- 

 turbance in the digestive processes. One criticism of the classic 

 experiment of Professor Chittenden^ with soldiers was that the amount 

 of nitrogen excreted in the feces of a group of men, presumably with 

 low diet, varied within very wide limits from that which would be 

 expected, or was regularly found with normal individuals. This 

 suggested the possibility, at least, that a restriction in protein had 

 resulted in an actual disturbance of the digestion processes. It there- 

 fore became necessary with our subjects to make periodic, so-called 

 ''digestion experiments.' ' 



These digestion experiments were made with two purposes in view: 

 (1) to note abnormalities if they existed, and (2) to give positive in- 

 formation as to the amount of unoxidized material leaving the body 

 from the alimentary tract. Theoretically, it would have been best 

 to have had a collection of feces throughout the entire time, but this 

 presented technical difficulties which were so great as to make such 



^ Chittenden, Physiological economy in nutrition, New York, 1907, p. 131. 



