CALCULATION OF RESULTS. 89 



CALCULATIONS FOR NITROGEN. 



It will be noted that at the top of the sheet (p. 84), the first space 

 below the heading is arranged for the calculation of the amount of 

 nitrogen. The amount of nitrogen in liters found, either by analysis 

 or calculation, in the chamber at the beginning of the experimental 

 period is first recorded. In case air has been rejected during the period, 

 as explained on page 67, the number of liters of air, the percentage 

 of nitrogen, and the number of liters of nitrogen thus lost are then 

 deducted. The negative correction for the amount of the nitrogen 

 removed with the absorbers and the positive correction for the amount 

 admitted with the oxygen are then added, together with a correction 

 for the interchange through the food aperture, if any, which may be 

 either positive or negative, according to whether nitrogen was admitted 

 or removed. On applying these corrections, the nitrogen present at 

 the end of the period is found. This value may then be transferred 

 to the next residual sheet under the heading "Volume of nitrogen in 



chamber at m liters," and serves as the basis of new nitrogen 



calculations until a new analysis has been completed. 



This method of calculation assumes that there is no free nitrogen 

 eliminated from the body other than that entering and leaving the 

 lungs in the free state ; in other words, that there is no production of 

 free nitrogen from food or body protein. That this is probably the 

 case, all experimental evidence thus far seems to show, although the 

 desirability of an absolute demonstration is obvious. 



Furthermore, it is assumed that there is no unaccounted-for leakage 

 of nitrogen into or out of the system. Indeed, as will be explained 

 beyond, this calculation is used ultimately to detect a leak. 



CALCULATION FOR TOTAL RESIDUAL OXYGEN. 



From the total volume of oxygen and nitrogen determined by de- 

 ducting the volumes of carbon dioxide and water from the total air 

 volume, V s , is deducted the volume of the nitrogen as computed at the 

 head of each residual sheet. In this instance, the volume of oxygen 

 plus nitrogen being 4,559.33, on deducting the computed residual 

 nitrogen, 3,574.58, the volume of oxygen was computed to be 984.75 

 liters. 



It is thus seen that if the corrected volume of air is known as well 

 as the volume of nitrogen, carbon dioxide, and water vapor, the differ- 

 ence is obviously the volume of oxygen. Since no other gases are 

 present in any considerable amounts, this method seems to suffice for 



