Water of Bespiration. 423 



day and during that time his muscular activity was much greater than in the 

 period inside the chamber, the losses in body-weight are in all probability too 

 large for the accurate computation of the water vaporized. From the loss in 

 body-weight and the carbon dioxide output, the water of respiration and per- 

 spiration was computed. The amounts thus found were for the 5 days 1058, 

 931, 662, 1329, and 803 grams. 



A much more desirable method of obtaining the water of respiration and 

 perspiration is that in which the subjects are inclosed in a respiration chamber 

 and the water-vapor in the ventilating air-current accurately measured. The 

 difficulties attending this determination are much greater than at first sight 

 would appear. The bedding and other articles inside the chamber are prone 

 to absorb or give off water and, indeed, in considerable amounts. To make a 

 complete determination of the amount of water-vapor eliminated from the 

 lungs and skin of the subject, therefore, necessitates, in addition to the 

 measurement of the water-vapor in the air, a record of the changes in weight 

 of bedding and other articles in the chamber. 



It is of special interest to note that the respiration chamber of Pettenkofer 88 

 was used first to study the metabolism of fasting man. The experiments were 

 made by Eanke." From the carbon dioxide output and the changes in body- 

 weight, Eanke computed the water of respiration and perspiration in three 24- 

 hour fasting experiments to be 609, 1080, and 537 grams. The room tempera- 

 tures were 19.5, 25.4, and 16.4, respectively. On the last day no water was 

 consumed. 



Direct determinations of the water-vapor output of fasting man were first 

 reported by Pettenkofer & Voit. 100 These writers early recognized the diffi- 

 culties attending water determination, and the observations regarding changes 

 in the weights of bedding, etc., are fully in accord with those of present day 

 experiments. 



The experiments of these investigators lasted 24 hours. During this period 

 the water determinations showed an elimination of 828.9 grams of water of 

 respiration and perspiration in one experiment and 814.1 grams in another. 

 In the third fasting experiment, during which, however, the subject engaged in 

 considerable muscular work, the water of respiration and perspiration amounted 

 to 1778.5 grams. While unquestionably the results obtained by Pettenkofer 

 & Voit are the resultant of a number of errors which are more or less com- 

 pensating, the fact remains that these observers recognized the desirability of 

 determining the water-vapor directly instead of computing the insensible loss, 

 and they also planned their experiments to cover 24 hours. 



The next successful attempt to determine directly the water-vapor eliminated 

 by fasting man was that of Sadovyen (2). Two experiments were made, one 



"Annalen der Chemie u. Pharm. (1862), n, Supplementband, p. 1. 

 w Archiv Anat. u. Physiol. (1862), p. 340. 

 100 Zeitsclir f. Physiol. (1866), 2, p. 478. 



