Heat Elimination and Production. 



193 



defined. As may be seen from this table, the heat production during sleep is 

 perceptibly increased by the preceding muscular activity, and within certain 

 limits this increase is approximately proportional to the amount of the activity. 



Table 76. Heat produced during sleep (1 a. m. to 7 a. m.J. 

 following different conditions of activity. 



[Average per hour.] 



1 Heat equivalent of work done 100 to 250 calories. 



2 Heat equivalent of work done 130 to 2S0 calories. 



3 Heat equivalent of work done 480 to 660 calories. 



4 Heat equivalent of work done 420 calories. 



5 Heat equivalent of work done 450 to 460 calories. 



6 Heat equivalent of work done 057 calories. Period of sleep, 4 a. m. to 7 a. m. 



These results point again to a stimulated metabolism and indicate that there 

 is an increased heat production accompanied by an increased katabolism as indi- 

 cated by the increase in the carbon-dioxide excretion and oxygen absorption. 

 While the difficulties pointed out previously in determining the heat production 

 during short periods are ever present, it is clear that the problem of the influ- 

 ence of previous muscular activity upon heat production during sleep is of 

 sufficient importance to warrant much further research. 



HEAT PRODUCTION DURING WAKING HOURS IN REST EXPERIMENTS. 



Direct measurements of the heat elimination or heat production were made 

 in experiments with 55 different individuals; with some of the subjects but 1 

 experiment was made, but with the majority there were 2 or more. The experi- 

 ments lasted from 3 hours to several days, and on the average the results ob- 

 tained were for a period of from 6 to 8 hours' duration. The influence of ex- 

 traneous muscular activity and minor muscular movements on the heat produc- 

 tion has been too often emphasized to need further discussion here. Since these 

 subjects were sitting up and not influenced by the enforced quiet of lying in 

 bed, there were considerable differences in the muscular activity, although the 

 subjects were not engaged in any extraneous muscular work and their move- 

 ments were confined to those minor muscular movements possible for a man 

 seated in a chair inside of a small respiration chamber. There was, however, 

 by no means as complete muscular relaxation and enforced muscular quiet as 

 that attending the experiments made in the laboratory of Zuntz and his asso- 

 ciates. The results of the experiments here reported are more nearly com- 

 parable with the results obtained by Sonden and Tigerstedt in that these inves- 



