16 Influence of Inanition on Metabolism. 



this air, the amount of water-vapor, and the amount of nitrogen enables the 

 amount of oxygen at the end of each experimental period to be computed 

 with great accuracy, and thus obviates the necessity of making the actual 

 analyses with potassium pyrogallate at the end of each period. In general, the 

 agreement between the computed oxygen content and that found by analysis is 

 very satisfactory. The loss in weight of the cylinder, therefore, corrected for 

 storage or loss cf oxygen from the air in the chamber, furnishes data for the 

 computation of the oxygen absorption during any given experimental period. 

 The measurements of respiratory gases in these experiments include the 

 cutaneous respiration as well as that of the lungs. The nitrogen of perspiration 

 is also determined in many instances. 



PHYSICAL MEASUREMENTS. 



The physical measurements incidental to experimenting on the transfor- 

 mations of matter and energy in the body consist generally of two kinds, first, 

 the measurement of the potential energy of the food, feces, and urine, and 

 secondly, the measurement of the heat elimination from the body. In certain 

 classes of experiments, where external muscular work is performed, measure- 

 ments of the heat equivalent of external muscular work are made. The present 

 series, however, consists entirely of rest experiments. 



Potential energy of food, feces, and urine. As a result of many experi- 

 ments of Eubner, Stohmann, Berthelot, and others, it is possible to compute 

 with reasonable exactness the energy equivalent of food, feces, and urine. 

 Improvements in the technique of the use of the bomb calorimeter, however, 

 have been adopted in this laboratory, and consequently the potential energy 

 of food, feces, and urine were, in every instance, actually measured by means 

 of the calorimetric bomb, 46 in that a dried portion of the material was burned 

 in oxygen under a pressure of 20 atmospheres. In the fasting experiments 

 the determinations were confined to those of the heats of combustion of 

 the urines, and a great deal of experimental work has been done upon this 

 subject. The most elaborate research on the heat of combustion of urine 

 is that published by Farkas and Korbuly. 47 Our experience has been that 

 the most concordant results have been obtained by drying in vacuo 10 to 15 

 cubic centimeters of urine with 50 mg. of salicylic acid and burning the 

 dried mass. The details of this investigation are not completed. They will be 

 published elsewhere. Unquestionably, the heat of combustion of urine is low 

 rather than high, since it is almost impossible to avoid the loss of ammonia or 

 the conversion of urea into ammonium carbonate, both of which result in a 

 loss of energy. The method outlined above gives results which, in our judg- 



40 Atwater & Snell, Jour. Amer. Chem. Soc. (1903), 25, p. 7. 

 "Archiv f. ges. Physiol. 1904), 104, pp. 564-607. 



