34 Influence of Inanition on Metabolism. 



of the chamber. There are about 1000 liters of oxygen in the air of the chamber 

 at the beginning of the experiment. The subject can draw upon this residual 

 for oxygen to support the vital processes and these drafts would of necessity 

 result in a difference in the composition of the air and the residual amounts 

 of the elements in it. Furthermore, the supply of oxygen admitted may at 

 times be larger than that actually consumed by the subject and hence the 

 residual amount of oxygen may increase. 



A reference to the original description of the methods and appliances for 

 the methods of determining oxygen 2 will show that the amount of oxygen 

 supplied varies with the barometric pressure. The admission of oxygen is 

 determined by the height of the rubber diaphragms on the two pans which 

 equalize the pressure of the air. If the barometer falls, the air in the chamber 

 expands, thus causing the rubber diaphragms to rise, consequently decreasing 

 the admission of oxygen during this period. The oxygen is being consumed out 

 of the air and a minimum amount is being supplied. Thus there is a draft 

 upon the residual quantity of oxygen. If the barometer rises the air inside 

 the chamber is compressed and diminishes in volume, resulting in a lowering 

 of the diaphragm on the pans. It becomes necessary, therefore, to so increase 

 the supply of oxygen as to keep the rubber diaphragm from touching the 

 bottom of the pans and thus eliminate any chance for a rarefaction inside the 

 chamber. Under these conditions the oxygen supplied to the chamber may be 

 much greater than that actually required by the subject and the residual amount 

 be thereby considerably increased. 



The determinations of the actual amounts of oxygen admitted to the system 

 and the variations in the residual amounts are recorded in table 7. Column a 

 records the per cent of oxygen in the air in the calorimeter chamber at the 

 end of each period, and the actual amount expressed in liters is tabulated in 

 column b. These amounts were obtained as a result of the analysis of air at 

 7 o'clock each morning and the computation of the amount of oxygen, which 

 takes into consideration the amount of water-vapor and carbon dioxide as 

 determined by the residual analysis, the amount of nitrogen added with the 

 oxygen, and the total air of the chamber. The only factor that is not shown 

 is the true volume of air inside the apparatus at the end of each period. While 

 this volume is in general not far from 4890 liters, there may be slight fluctu- 

 ations in volume, due to the size of the subject and number of miscellaneous 

 articles inside the chamber. From these data the amounts of oxygen remaining 

 in the chamber at the end of each period were readily computed. 3 



During the period from 4 to 7 a. m. on December 18, the preliminary night, 

 the increase in the amount of oxygen residual in the chamber amounted to 



2 Carnegie Institution of Washington Publication No. 42. 



3 For a detailed explanation of the method of computation, see U. S. Dept. Agr., 

 Office of Exp. Sta. Bui. 175. 



