422 Influence of Inanition on Metabolism. 



nature of clothing, furniture, etc., and difficulties attending the accurate record 

 of body-weight, all tend to vitiate the accuracy of the indirect determination of 

 water-vapor as heretofore made. 



To be sure, a fairly close approximation can be obtained by means of the 

 so-called " insensible loss," which can be computed from the changes in 

 body-weight from the beginning to the end of the day, the weights of urine 

 and feces, and the weights of drinking-water, provided there is a determination 

 of the amount of carbon dioxide exhaled. In the experiments on Cetti and 

 Breithaupt reported by Munk (7), the respiratory quotient and consequently 

 the carbon dioxide elimination was determined on different days but only 

 for short periods each day. From these determinations, the authors calcu- 

 lated the total carbon dioxide elimination for the 24 hours. Thus, the data 

 were obtained for computing the insensible loss in these experiments. 



In the 10 days of Cetti's experiment, it was computed that there were 8016 

 grams of water of respiration and perspiration, an average of 802 grams per 

 day. 97 From the determinations of the amount of protein katabolized, and like- 

 wise from the estimations of fat oxidized, on the basis of the respiratory ex- 

 periments made with the Zuntz apparatus, the authors apportioned the amount 

 of water vaporized in terms of water of oxidation of organic material and water 

 lost from the body itself. Similar results were reported for Breithaupt in a 

 6 days' fast in which there were 4199 grams (700 grams per day) of water of 

 respiration and perspiration. 



The errors involved in computing the daily absorption of oxygen and 

 elimination of carbon dioxide from respiration experiments lasting but 10 to 20 

 minutes are obvious, and the errors which affect the measurement of the carbon 

 dioxide elimination likewise affect the estimations of the water of respiration 

 and perspiration. Nevertheless, the results obtained by this method are by 

 no means as inaccurate as one might suppose. 



By means of the more accurate determination of the total elimination of 

 carbon dioxide with the Tigerstedt apparatus, the water of respiration and 

 perspiration was computed in the experiments on J. A. (9). The objections 

 to the determination of carbon dioxide in short periods did not here obtain, 

 and although the subject left the respiration chamber each day for a period of 

 two hours, the estimation for the remainder of the day was unquestionably 

 extremely accurate. When computed for the 24 hours of the day, the result 

 represents the probable carbon dioxide output of a fasting man under the con- 

 ditions of muscular activity obtaining while in the respiration chamber. An 

 important factor in the indirect determination of the amount of water of 

 respiration and perspiration is, however, the change in body-weight. Since 

 the subject J. A. was outside the respiration chamber at least 2 hours of the 



" (7), p. 114. 



