INTRODUCTION. 11 



individuals of the same weight and age, sleep, and the after effect of 

 exercise, all have an influence upon the basal metabolism, the conclusion 

 was drawn that the basal metabolism of an individual is a function, first, 

 of the total mass of active protoplasmic tissue and, second, of the stimu- 

 lus to cellular activity existing at the time the measurement of the metab- 

 olism was made. It was furthermore maintained that ''apparently at 

 present no law can be laid down that will cover both of these important 

 variables in the basal metabolism of an individual."^ 



STUDY OF FACTORS TENDING TO LOWER METABOLISM. 



In our study of variations in basal metabolism, special consideration 

 has been given to the question of those factors which tend to lower the 

 metabolism, and it was early recognized that prolonged fasting pro- 

 duced such an effect. The results obtained at the Nutrition Laboratory 

 during the 31-day fasting experiment^ on the subject L. are decisive on 

 this point. Here the analysis was first made upon the basis of per 

 kilogram of body- weight and per square meter of body-surface; the 

 body-surface was computed by the old formula of Meeh. By both 

 methods of computation, definite loss in heat production was found as 

 the fast progressed, save that after the fourteenth or fifteenth day there 

 was a tendency to constancy. A subsequent revision of the calcula- 

 tions of body-surface, based upon a series of photographs and the more 

 modern Du Bois measurements,^ confirmed the earlier findings and 

 placed them upon a more scientific basis. 



A somewhat complex factor entered into the interpretation of the 

 values for the basal metabolism of this fasting man in that a definite 

 acidosis developed. Although we believe that acidosis tends to stimu- 

 late the metabolism and thus would partly offset the depressing effect 

 of the fasting per se, nevertheless there is no question but that the 

 metabolism per kilogram of body-weight or per square meter of body- 

 surface was distinctly lowered as a result of fasting. Of particular 

 significance is the fact that with this fasting man there was no propor- 

 tionate loss of strength but a general feeling of unimpaired mental and 

 physical activity. While the subject showed a faUing off in the dyna- 

 mometric tests, from a superficial observation one would never realize 

 that the man had been without food for 31 days. In talking to a group 

 of medical men on the thirty-first day of his fast, he exhibited all the 

 vivacity, strength of voice, and vigor of gesture that an ordinary 

 individual would use. We thus have here evidence of a depressed 

 metabolism unaccompanied by marked loss in intellectual or physical 

 powers. It was demonstrated, therefore, that a specific factor, namely, 

 complete inanition, can produce a definite and thoroughly established 

 lowering of metabolism. 



1 Benedict, Journ. Biol. Chem., 1915, 20, p. 299. 



* Benedict, Carnegie Inst. Wash. Pub. No. 203, 1915. 



' Benedict, Am. Journ. Physiol., 1916, 41, p. 292. 



