48 FOOD INGESTION AND ENERGY TRANSFORMATIONS. 



the professional bicycle rider studied by us 1 and also the one studied 

 by Benedict and Cathcart 2 showing no difficulty in producing such 

 increases. With values so large as these, it is clear that small differ- 

 ences in the base-line play a comparatively unimportant role. Indeed, 

 it has been the custom in the researches on muscular work, published 

 not only from this laboratory but also by investigators elsewhere, to use 

 a basal value determined with the subject lying down but not asleep. 

 While such a practice is theoretically unsound, the increments due to 

 muscular work are so large that in comparisons of metabolism during 

 muscular work and during rest the relatively slight differences between 

 metabolism during sleep and that with the subject standing or sitting 

 quietly or lying down awake may be neglected. 



In studies on the influence of food upon metabolism, the increments 

 are much smaller than in studies with muscular work. A glance at 

 the literature (see pages 10 to 46) shows that the maximum effect due 

 to this factor may be to increase metabolism for a short time, possibly 

 30 or even 40 per cent. When we consider the potential increment of 

 1 ,000 or more per cent with muscular work, even this maximum increase 

 in metabolism after food seems comparatively insignificant. Accord- 

 ingly, in a study on the effect of the ingestion of food, great care should 

 be taken to secure a uniform base-line and a critical examination should 

 be made of those factors liable to influence the determination of the 

 basal metabolism. 



The quiescent metabolism of the body may be affected by a 

 number of factors, primarily by muscular activity. We have already 

 seen that severe muscular work increases the metabolism largely, but 

 we find that moderate activity or even the relatively few muscular 

 movements that distinguish between complete rest and ordinary rest 

 also have a definite influence. Furthermore, when the increment in 

 metabolism to be measured is probably small, one has to consider not 

 only minor muscular activity, but even the degree of muscular relaxa- 

 tion. Thus we find Johansson 3 training himself and his co-workers to 

 establish an arbitrarily complete muscular repose. Finally, experi- 

 mental evidence 4 obtained in the Nutrition Laboratory has shown 

 positively that the quiescent metabolism of a subject asleep differs con- 

 siderably from that of the same subject awake. In experiments with 

 the subject in a profound sleep there was a noticeable decrease in pulse 

 rate, which was almost invariably accompanied by a decrease in total 

 metabolism. We may expect, therefore, that with the subject in deep 

 sleep there will be a decrease in pulse rate, respiration rate, and muscle 

 tonus, with consequently lower metabolism as compared with values 



'Benedict and Carpenter, U. S. Dept. Agr., Office Exp. Stas. Bull. 208, 1909. 

 "Benedict and Cathcart, Carnegie Inst. Wash. Pub. No. 187, 1913. 

 'Johansson, Skand. Arch. f. Physiol., 1S9K, 8, p. 119. 

 'Benedict, Carnegie Inst. Wash. Pub. No. 203, 1915, p. 343. 



