Heat Elimination and Production. 199 



of noting the increase or decrease in the water condensed upon the pipes. In 

 the form of apparatus used at Wesley an University, provisions for these weigh- 

 ings were made and in practically all experiments, especially work experiments, 

 the weights were taken. In the early reports, the importance of these weighings 

 was overlooked and unfortunately computations were based only upon the water- 

 vapor leaving the chamber as such, while as a matter of fact, a very large 

 amount of water-vapor was distilled, so to speak, from the man's body upon the 

 cold heat-absorbers; consequently, the proportion of total energy required to 

 vaporize water from the lungs and skin was indicated as considerably less than 

 was actually the case. In discussing here, therefore, the influence of muscular 

 work upon the proportion of total heat required to vaporize water from the lungs 

 and skin, we deal not only with water vaporized and leaving the chamber in the 

 air-current, but the total water vaporized from the lungs and skin of the subject. 

 Water may be carried out of the chamber in the air-current as water-vapor and 

 during rest experiments is chiefly, if not wholly, withdrawn in this way, and 

 yet the water vaporized from the body during work experiments is in large part 

 condensed upon the cooling surface of the heat absorbers. 



In the investigations here reported, with at least 5 subjects we have experi- 

 ments showing conditions of varying muscular activity. With 3 of these, the 

 muscular activity can be characterized as severe and very severe. In table 80 

 are recorded the total heat elimination, the water of respiration and perspira- 

 tion, the heat used to vaporize water from the body, and finally the proportion 

 of the total heat used to vaporize the water from the lungs and skin. 



In the rest experiments in table 80 it is seen that the proportion of the total 

 amount of heat used to vaporize water is substantially that ascribed to the 17 

 subjects in the preceding table, namely, 23 per cent. During moderate work, 

 the heat equivalent of the external work done being from 130 to 280 calories, 

 the proportion of total heat used to vaporize water increases to 27.8 and 34 

 per cent respectively. If the subject is engaged in severe muscular work 

 muscular work equivalent to 420 to 6C0 calories the proportion of the total 

 amount of heat used to vaporize water from the lungs and skin increases to 

 approximately 40 per cent, and in 2 experiments where the subject was engaged 

 in very severe muscular work equivalent to 957 to 1482 calories, with a total 

 heat production amounting in one instance to 7137 calories in 24 hours and in 

 the other to 9314 calories, the proportion of the total heat production required 

 to vaporize water from the lungs and skin rises to 48 per cent. Thus, while 

 in rest experiments but a small portion of the heat produced is required to 

 vaporize water from the lungs and skin, as the muscular activity increases there 

 is a very much larger proportion required and as the work increases, the most 

 important factor in the increment is the heat absorbed as a result of the 

 increased vaporization of water. 



It is furthermore clear from this table that as the heat production increases 

 as a result of muscular work, the increase is almost equally divided between 

 14 



