-.on Influence of Inanition on Metabolism. 



Proportion of oxygen consumed, carbon dioxide and water eliminated, and 

 heat produced during different periods. The variations in the amounts of the 

 four factors oxygen, carbon dioxide, water, and heat which occur during 

 the different periods of the day are recorded in terms of per cents in table 240. 



A certain parallelism appears in the proportions of these four factors; thus, 

 the largest katabolic activity occurs, as a rule, during the first period of the 

 day when more oxygen is consumed and carbon dioxide and water given off 

 and heat produced than during any other period of the day. A close examina- 

 tion of the figures shows that in the 2-hour periods during the night from 

 1 to 7 a. m., the results from period to period are on the whole more nearly 

 constant than during those of any other 6 hours. As has been shown in the 

 foregoing discussion, the influence of external muscular activity is compara- 

 tively unimportant in its effect on the total heat production of a fasting man 

 at rest. The results further show that although fluctuations in the pulse rate 

 (assumed to be due to changes in the work of circulation) do not account for 

 the marked differences in the accompanying heat production, nevertheless the 

 pulse rate has been found to be a remarkably good index of the rise or fall in 

 the amount of heat produced. The external muscular activity as well as the 

 pulse rate is usually lowest during the period from 1 to 7 a. m. 



During periods of sleep major muscular movements were not impossible, but 

 it is probable that in general the subjects were in about the same degree of 

 muscular activity in all the experiments. It is quite probable that extraneous 

 muscular exertion can be neglected, although undoubtedly on certain nights, 

 when the subjects reported a poor night's sleep or the physical assistant 

 recorded unusual muscular activity, the external muscular activity did have 

 an influence on the total katabolism. It is of especial interest to study the 

 four important factors during this night period. For purposes of comparison, 

 the amount of oxygen consumed, carbon dioxide and water given off, and heat 

 produced per minute, are computed from 1 to 7 a. m. in all the experiments 

 with and without food. These results are given in table 241. 



The striking feature of these comparisons is the fact that in the longer 

 experiments, except No. 77, which was abnormal in this and other respects, 

 during the night period when the muscular activity is at the minimum, there 

 is a progressive diminution in the total katabolism as indicated by the con- 

 sumption of oxygen, the elimination of carbon dioxide and water-vapor, and 

 the production of heat. This observation is also true when the computations 

 are made on the basis of per kilo of body-weight or per square meter of body 

 surface. 



