196 Metabolism of Healthy Man. 



seated in a chair. The extraneous muscular activity is confined to moving 

 somewhat in the chair, standing occasionally to go to the food aperture, a 

 movement that has received definite study, (see page 61 of this report) and, 

 during longer experiments, going to bed and rising. The minor muscular 

 movements incidental to taking the food and dishes from the food aperture, and 

 collecting the feces and urine, are likewise included. These minor muscular 

 movements were of course made by many of the subjects and yet in practically 

 all of the experiments reported in this table, the muscular operations during 

 waking hours were for the most part comparable on different days and witli 

 different subjects. The only variation was in the taking of food, since some of 

 the subjects partook of food and others did not. The influence of these special 

 factors upon metabolism, however, is to receive special treatment in a subse- 

 quent portion of this report and need not be further dwelt upon here. 



PROPORTION OF TOTAL HEAT ELIMINATION REQUIRED TO VAPORIZE WATER FROM 



LUNGS AND SKIN. 



Heat may leave the body in several ways, by radiation and conduction from 

 the surface, by warming the inspired air, by the heat of vaporization of water 

 from the lungs and skin, and by the sensible heat of excreta. The measure- 

 ments made with the respiration calorimeter and accessory apparatus permit 

 the apportionment of the total heat elimination to certain of these various paths. 



During Sleep and during Waking Hours in Rest Experiments. 

 Inasmuch as the determination of the water vaporized from the lungs and 

 skin is included in practically all experiments with the respiration calorimeter, 

 one of the most prominent of these apportionments is the calculation of what 

 part of the total heat output is required to vaporize this water. The subject 

 has received considerable attention in the earlier publications from the chemical 

 laboratory of Wesley an University and in table 79 we have collected the results 

 obtained on 17 subjects during sleep and during waking hours. For the most 

 part the values are obtained directly from the heat elimination rather than 

 from the heat production, for the proportion of the heat lost through the water 

 vaporization bears a relationship not to the heat production but to the heat 

 elimination. In a few instances, the heat production rather than the heat elimi- 

 nation is included, but in 24-hour experiments, or even in 6-hour experiments 

 made under the conditions obtaining in these experiments, the heat elimination 

 and heat production are usually almost identical, and it has not been deemed 

 advisable to engage in a long calculation to separate carefully the experiments 

 including the heat production from those in which only the heat elimination is 

 given. For purposes of comparison, we believe it is reasonable to assume that 

 the values are fairly indicative of the heat elimination. During sleep it can be 

 seen that on the average 27 per cent of the total heat eliminated is required to 

 vaporize the water from the lungs and skin. This percentage varies from 20 to 



