Variations in Metabolism. 211 



VARIATIONS IN METABOLISM DUE TO VARIATIONS IN 

 MUSCULAR ACTIVITY. 



COMPARISON OF THE METABOLISM WHILE LYING AWAKE WITH METABOLISM 



DURING SLEEP. 



The complete relaxation of the musculature during sleep results in a very low 

 metabolism. When lying awake, certain individuals have been able by training 

 to simulate this relaxation of the muscles to such an extent that the carbon- 

 dioxide production, the only factor measured, has been lowered to practically 

 that during sleep. The experiments of Johansson * in Stockholm have been 

 cited frequently to illustrate the fact that with complete muscular relaxation, 

 the carbon-dioxide production may be the same as that of sleep. Experiment- 

 are made with the Zuntz-Geppert apparatus when the subjects are lying awake 

 with complete muscular relaxation, but this apparatus does not permit satis- 

 factory experiments when the subjects are asleep. In certain of the experi- 

 ments here reported, plans were made to study the metabolism when lying awake 

 in the forenoon covered with a blanket on a cot and to compare the metabolism 

 during this period with that of the period from 1 a. m. to 7 a. m. when the 

 subjects were in the same body-position but in all probability asleep. These 

 experiments, however, are not easily compared. It is very difficult to secure 

 satisfactory experiments of this kind, but G have been collected as indicating in 

 a general way the variations in metabolism. Of these 6, 3, we believe, should 

 not be considered as strictly comparable, since the lying-awake period did not 

 immediately follow the sleeping period and other factors affecting metabolism 

 may have had an influence. They are reported in table 101, but are left out of 

 the average. The other 3 (2 with the subject H. C. K. and 1 with the subject 

 H. E. D.) are strictly comparable. The subjects slept during the night and 

 the next morning remained in bed instead of rising. The metabolism during the 

 morning period was, therefore, measured under practically the same conditions 

 as during the night, except that the subjects were awake. In this way we ob- 

 tained the best possible comparison of the metabolism under the two conditions. 



With the three subjects A. H. M., C. E. Y. and J. H. K. we find that there 

 is an increase in the metabolism during the lying-awake period as compared 

 with the period when the subject lay asleep amounting to over 25 per cent on 

 the average for the carbon-dioxide excretion, nearly 30 per cent for the oxygen 

 absorption, and about 25 per cent for the heat production. The water vaporiza- 

 tion shows very wide fluctuations, but as has been frequently pointed out in a 

 previous discussion, it is without significance. With the three more strictly 

 comparable experiments we find an increase on the average of 10 per cent in the 

 carbon-dioxide excretion, practically no change in the water vaporization, 4.T 

 per cent in the oxygen absorption, and 11. -1 per cent in the heat production. 



From these experiments, therefore, it can be stated that there is a material 

 increase in the metabolism when the subject is lying awake over that when lying 



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



