116 Metabolism of Healthy Man. 



of which the products of respiration from the lungs were withdrawn imme- 

 diately and carried out of the chamber, and consequently he breathed the air 

 of the chamber non-contaminated by carbon dioxide or water from the lungs. 

 There was, however, the water vaporized from the skin. On this day, when 

 the relative humidity was not far from 30 per cent, the insensible perspiration 

 amounted to 60 grams per hour. On the second day, the subject wore no mask, 

 but the conditions of ventilation were such as to allow the carbon dioxide to 

 increase enormously inside the chamber. During this time there was a con- 

 densation of water on the surface of the heat-absorbers, and hence there was 

 a larger relative humidity (about 60 per cent) during this day of the experi- 

 ment. On the third day, when the ventilating conditions were substantially 

 those ordinarily obtaining in metabolism experiments with the respiration 

 calorimeter, the average humidity was not far from 50 per cent. The insensible 

 perspiration for the last 2 days was 33 and 26 grams per hour, respectively, 

 the variation for the whole experiment being from 60 to 26 grams per hour. 

 Variations with the same individual. There are, however, as an inspection 

 of the table will show, noticeable differences in different experiments with the 

 same subject, such as can be explained only by assuming that the larger insen- 

 sible loss is the result of increased total metabolism accompanying increased 

 minor muscular activity. An examination of the data obtained with especially 

 well-trained subjects, who endeavored to adjust the muscular activity from 

 day to day so as to have all the experiments strictly comparable, shows that, 

 while the insensible loss may vary considerably with different individuals, with 

 the same individual under like conditions of experimenting the loss is relatively 

 constant. This is nowhere more strikingly shown than in the results with the 

 subject, S. A. B., with whom experiments covering 27 days were made. The 

 insensible loss varies from 23 to 35 grams per hour, and excluding the first 2 

 days of experimenting, the variation was from 23 to 29 grams per hour. 



Average Insensible Loss Per Hour During Rest. 



While, therefore, the insensible perspiration may with muscular work rise 

 as- high as 276 grams per hour, it is seen that in this large number of rest 

 experiments there is a variation from 23 to 79 grams per hour. The average 

 of 158 days, covering 2150 hours, shows that the insensible perspiration of 

 normal healthy men, sitting, lying asleep or awake, or engaged in minor 

 activities, is 40 grams per hour. 



NATURE OF THE INSENSIBLE PERSPIRATION. 



When the body is not being supplied with either drink or food, and when no 

 urine or feces are passed, the body-weight continues to decrease by virtue of 

 the fact that there is a constant loss of material, i. c, water-vapor and organic 

 material that is oxidized to water and carbon dioxide. In reality the insensible 



