436 Influence of Inanition on Metabolism. 



From the data recording the water determinations of the air residual in the 

 chamber and the temperature of the air, the relative humidity is obtained 

 and it is therefore possible to compute the total amount of water-vapor in the 

 air taken into the lungs. Assuming that the air leaves the lungs saturated 

 with water-vapor at the body temperature of 37, the total amount of vapor 

 in the expired air may thus be computed. Deducting the amount in the air 

 inspired from that in the air expired, the water-vapor taken up by the air as it 

 passes through the lungs is readily obtained. 



The data are presented in table 220 herewith, in which the first column 

 shows the total ventilation of the lungs, the second, the water in the inspired 

 air, the third, the water in expired air, and the fourth the water eliminated 

 from the lungs. If this last amount be deducted from the total water of 

 respiration and perspiration, the water eliminated from the skin is obtained. 

 This is recorded in column e. In the last two columns of the table the pro- 

 portions of total water vaporized from the lungs and from the skin are given. 



It will be seen that this method of computation involves two assumptions 

 first, that the total ventilation of the lungs is 21 times the volume of oxygen 

 absorbed, and second, that the air leaving the lungs is saturated with water- 

 vapor. Eegarding the first of these assumptions, it is probably true that with 

 certain individuals this factor may be wrong, but it is highly probable that in 

 the large number of experiments here averaged the factor is reasonably correct. 

 Eegarding the second factor Eubner m has shown that with forced respiration 

 during muscular work, the air leaving the mouth and nose may not be satu- 

 rated with water-vapor at the temperature of the body. Eecently Lesage us 

 has, by means of a respiratory hygrometer, computed the water-content of 

 the expired air from the dew point obtained by means of his apparatus. With 

 ordinary respiration the tension of the water-vapor is found to be 36.9 mm. 

 Since the expired air has a temperature of 36.5, corresponding to a maximum 

 tension of 43.1 mm., the author contends that the air is not saturated with 

 water-vapor. While, therefore, this second assumption may be erroneous, for 

 the want of more accurate data, it seems undesirable to make any correction for 

 these values. If Lesage is correct, the result will be to lower the estimated 

 amounts of water-vapor eliminated from the lungs. 



The amount of water-vapor eliminated from the lungs is in most instances 

 somewhat less than that from the skin. In some experiments, notably in 

 experiment No. 80, it is but 30 per cent of the total water elimination, while 

 in other experiments, for example, food experiment No. 74, it is over 50 per 

 cent. Marked differences are noted between different subjects, especially in 

 the longer experiments. In the series of 2-day experiments, these differences, 

 aside from experiment No. 80, practically disappear. 



111 See discussion by Magnus-Levy, Physiologie des Stoffwechsels (1905), p. 426. 

 lu Compt. rend. 136, 1097. 



