Water of Kespiration. 433 



this particular period in greater amounts than in any other period. This 

 latter factor may likewise partially explain the tendency for the water output 

 to be less during the night, since there may be an accumulation of water in the 

 bedding. 



Excluding the period from 7 a. m. to 9 a. m., the average amounts of water- 

 vapor eliminated from the lungs and skin per 2-hour period remain singularly 

 constant, varying from 59.5 in the period 9 a. m. to 11 a. m. to 55.6 from 3 

 a. m. to 5 a. m., a difference of less than 7 per cent. On the whole, the greatest 

 water elimination takes place during the waking hours and the smallest during 

 sleep. 



In the recent study of the periodic elimination of water-vapor by Wolpert 

 & Peters, 108 a much greater variation in the water vaporized is shown per hour 

 than in the averages of these experiments. This, however, is to be expected 

 since their observations were confined to but three experiments. In their 

 experiments the attempt was made to obtain the correction for the changes m 

 weight of the clothing and bedding at the end of each experimental period, 

 which was of 4 hours' duration. To accomplish this, the subject of the 

 experiment removed the clothes and weighed the bed, bedding, and clothing at 

 the end of each period. While, theoretically, this procedure is well designed 

 to give accurate data regarding the water-vapor output, practically, the extra- 

 neous muscular activity of dressing and undressing and weighing the clothing 

 is an abnormal one in experiments in which the water-vapor output during rest 

 is to be studied. Furthermore, during the period when the clothing is removed, 

 water is rapidly vaporized from the body as well as from the clothing, and 

 hence there is a vaporization of water much greater than would normally 

 occur with the subject clothed and resting quietly. It is thus seen that the 

 two series of experiments can hardly be compared, although it may readily be 

 contended that the results of the experiments here reported represent more 

 nearly what would be expected to be the water-vapor output of the resting man. 

 This is especially true of the first day of fasting. The factors entering into 

 the later days of fasting obviously would affect the elimination of water-vapor 

 to such a degree that the averages of all these experiments would be distinctly 

 lower than what could be considered a normal for the resting man. Consider- 

 ing only the first day of fasting, the water-vapor output is still noticeably 

 greater during the first period of the day and, aside from this period, it is 

 somewhat larger per hour during the day time than that during the night. 



Eecognizing the well-known effect of activity on the water-vapor output, it 

 is reasonable to suppose that in these fasting experiments, the large output 

 during the first period may in part at least be accounted for by the extraneous 

 muscular effort. Experiments for the study of the true water-vapor output 

 of resting man should be so designed as to insure regularity of muscular 



1M Archiv f. Hygiene (1906), 25, p. 299. 

 28 



