146 



Metabolism of Healthy Man. 



Apportionment to Lungs and Skin during Waking Hours. 



The relative amounts of water vaporized from the lungs and skin during 

 waking hours in the experiments reported in the first part of this publication, 

 as well as in many of the earlier experiments, have been computed and tabu- 

 lated in table 56. The method of computing one experiment is here given. 



Table 56. Proportions of total water vaporized from the Jungs and skin, 

 respectively, during waking hours in rest experiments. 



During the waking hours in the experiment of April 18, 1903, W. O. A., 

 absorbed 276.6 liters of oxygen. According to the Zuntz factor, 21, the total 

 ventilation of the lungs during this period was therefore 5809 liters. In order 

 to know the amount of water-vapor taken into the lungs by the air, it is 

 necessary to know the absolute moisture-content of the air inspired. This 

 is obtained from an analysis of the residual air in the chamber. It was found 

 that during the waking hours of this experiment the average quantity of water- 

 vapor remaining in the chamber was 48.7 grains. The volume of the chamber 

 was approximately 4900 liters. The total water in the air inspired may, there- 

 fore, be obtained as follows: 48.7 -f- 4900 X 5809 = 57.7. Consequently, dur- 

 ing this period it is considered that the inspired air contained 57.7 grams of 

 water-vapor. In order to compute the amount of water-vapor expired, it is 

 assumed that the air leaving the lungs is saturated at the temperature of the 

 human body, namely, 37 C. One cubic meter of air saturated with water- 

 vapor at 37 C. contains 43.465 1 grams of water, and the total amount exhaled 

 by the man is computed as follows : 43.465 X 5809 -4- 1000 = 252.5. The 

 total amount of water-vapor leaving the body in the exhaled air is, then, 252.5 

 grams. Deducting from this the amount in the air inspired, namely, 57.7 

 grams, we have as the total amount of water- vapor leaving the lungs, 194.8 



1 Smithsonian Physical Tables, Washington, 1896, p. 155. 



