Water Output. 421 



water of feces. 



From the discussion of feces (see page 337), it can readily be seen that the 

 isolation of so-called " fasting feces," namely, feces, the organic matter of 

 which may be said to be derived from the disintegration of body material, is 

 extremely difficult. The excretion of water in feces, however, can be readily 

 determined. Unfortunately, careful determinations of water in feces were 

 not made in some of the Middletown experiments, since it was apparent that 

 the feces had resulted from the ingestion of food prior to the fast. Errors are 

 thereby undoubtedly introduced, since the water of the feces was actually 

 excreted. In the food experiments, it has been assumed that certain amounts 

 of water were excreted in this way, and the preformed water lost has been 

 calculated on this assumption. 



While normal feces contain not far from 70 to 80 per cent of water, during 

 fasting, the feces are usually retained for a considerable period of time, become 

 hard and pilular, and consequently have a much smaller water content. The 

 exigencies of experimenting in one instance called for the removal of fecal 

 matter by means of an enema, and hence in this connection it was difficult to 

 determine the water actually excreted with the feces. 



WATER OF URINE. 



Large amounts of water are excreted in the urine during fasting. In a 

 preceding section the ratio of water of urine to water of drink has been 

 discussed at length (see p. 348). 



WATER OF RESPIRATION AND PERSPIRATION. 



Considerable quantities of water are evaporated from the lungs and skin 

 and it becomes necessary in accurate metabolism experiments to measure the 

 amounts lost. Since each gram of water vaporized requires the absorption of 

 0.592 calorie of heat, the influence of the water of respiration and perspiration 

 on the heat output is very marked, and consequently for the accurate determina- 

 tion of the heat production careful measurement of the water of respiration 

 and perspiration is necessary. Furthermore, an accurate record of the water of 

 respiration and perspiration is essential for determining the amount of pre- 

 formed water excreted, and the water resulting from the oxidation of organic 

 material in the body. 



The difficulties attending the collection and analysis of the respiratory gases 

 have precluded, in practically all of the earlier experiments on fasting, a study 

 of the amounts of water vaporized from the lungs and skin. Although the 

 amount of carbon dioxide has been frequently determined, unusual difficulties 

 attend the accurate measurement of loss of water from the body. The fluctua- 

 tions in the relative humidity inside the respiration chamber, hygroscopic 



