170 Metabolism of Healthy Max. 



The foregoing statement shows very strikingly the variation in carbon- 

 dioxide excreted by different individuals, even under like conditions of muscu- 

 lar activity and rest. It must be borne in mind that the experiments from 

 which these data were drawn were made during the period from 1 a. m. to 

 7 a. m., when the subjects were supposed to be covered and quietly lying asleep 

 in the respiration chamber. In the large majority of instances they had been 

 accustomed to the chamber for some time previous, and we have every reason 

 to believe that the sleep was normal and somewhat profound. 



The question as to whether sleep per se has any influence upon metabolism 

 has been considered in great detail by Johansson, 1 who, as a result of a most 

 rigid series of experiments, by voluntary control of muscular movements was 

 able to reduce the carbon-dioxide production to practically a constant value 

 throughout the whole 24 hours. In all probability, outside of the possibilities 

 of more complete muscular relaxation and quietude, sleep of itself has no 

 influence on metabolism. As may be seen in a later discussion, any factors 

 that reduce muscular tonus or decrease the respiration-rate or heart-beat tend 

 to decrease the metabolism, and in so far as sleep produces these results, it can 

 possibly be considered as directly affecting metabolism. It is apparent, there- 

 fore, from the results of the experiments here reported, that the problem of 

 metabolism during sleep presents many interesting features, but it is also 

 obvious that experiments during sleep should be accompanied by careful re- 

 cords of the pulse- and respiration-rates, and, if possible, of the blood-pressure 

 and bodily movements, in order to make the value comparable. Due regard 

 should be given to the preceding diet, and of prime importance also, in studying 

 the carbon-dioxide excretion are the chemical data which will allow the appor- 

 tionment of the oxidation between glycogen and fat during the resting period. 

 Until all of these conditions are met with results can have but a tentative value. 



CARBON-DIOXIDE ELIMINATION DURING WAKING HOURS. 



From the results of the consideration of the carbon-dioxide production during 

 sleep it is easy to conceive that differences in the amounts of carbon dioxide 

 excreted by individuals during waking hours may be very great, even under 

 conditions approximating uniformity so far as muscular activity and diet are 

 concerned. 



Although the experiments from which these data are derived were so-called 

 rest experiments, i. e., with no external muscular work, the variations in the 

 amount of carbon dioxide produced are noticeable. The men were supposed, 

 for the most part, to be sitting quietly in a chair or moving about the narrow 

 confines of a small respiration chamber during the day. In certain experiments 

 the men remained seated during the whole day. In others, they lived more or 

 less normally, but were required to move occasionally, as to go from the chair 

 to the food aperture, to lie down at times on the bed, or to rise and sit in the 



1 Johansson, Skand. Archiv f. Physiol., 1898, 8, p. 85. 



