TECHNIQUE FOR METABOLISM DURING REST. 91 



The apparatus and breathing appliance used, the date, and the num 

 ber of the experimental period are first recorded, also the subject's 

 name. The times of beginning and ending the experiment are like- . 

 wise recorded, that is, the exact moment the valve is turned connecting 

 or disconnecting the subject with the au'-current. The duration of the 

 two measurements of oxygen are given, the figures in parentheses show- 

 ing these times with the seconds reduced to decimals for convenience in 

 calculating. 



In the middle section records are made of the height of the spirometer 

 bell and the temperature of the spu-ometer (°F.) at the beginning and 

 end of the complete period and the intermediate period. From these 

 records the average temperature (centigrade) of the spirometer and 

 change in height of the spirometer bell are calculated for the two meas- 

 urements. 



In the lower section the cubic centimeters of oxygen per minute are 

 computed by logarithms. The decrease in the volume of air is first 

 calculated from the difference in height of the spirometer bell by means 

 of the factor for this spirometer (20.92 c.c. for each millimeter of change) , 

 then reduced to 0° C. and 760 mm. pressure, using the average temper- 

 ature of the spirometer during the measurements and the barometer 

 record obtained for the period. Thus the logarithm of the spkometer 

 difference for the total period (164 nrni.) is 2.21484; the number of cubic 

 centimeters represented by each millimeter of difference for this spirom- 

 eter is 20.92, with a logarithm of 1.32056. The logarithm for the fac- 

 tor used to reduce the average temperature of the spirometer to 0° C. 

 (9.96071 — 10) and that for the factor to reduce the observed pressure 

 to 760 mm. (9.98877 — 10) are also found from tables prepared for the 

 purpose. The total of the four logarithms gives the logarithm (3.48488) 

 for the decrease in volume of the air in the apparatus during the period, 

 at 0° C. and 760 mm. pressure, this being equivalent to the volume 

 of oxygen consumed. No correction is made in this calculation for 

 the tension of aqueous vapor, as it is assumed that the air as measured 

 is dry.^ From the logarithm of this volume is subtracted the logarithm 

 1.18384 for the duration of the measurement (15' 16"), the result giving 

 the logarithm for the cubic centimeters of oxygen consumed per min- 

 ute, in this case 200 c.c. 



A further correction in the results obtained by this method of calcu- 

 lating is necessary, inasmuch as the total volume of air in the spirom- 

 eter and air system should be reduced to 0° C. and 760 mm. pressure at 

 the beginning and end of the period to obtain the true shrinkage in the 



1 For the measurement of the total period, this assumption is correct. During the measure- 

 ments in the intermediate period (a) made by the Emmes method, there is unques- 

 tionably a certain amount of moisture in the air. Theoretically corrections should be 

 made for this moisttire. It has been shown, however, by means of a sensitive psychrom- 

 eter placed in the air-circuit, that the percentage of moisture is so small that in prac- 

 tice it may be neglected in the calculation of the oxygen consumption during these short 

 periods. 



