The calculation of the carbon dioxide produced was a relatively simple matter. The apparent volume of the chamber was corrected for any change in the level of the spirometer, this correction being 21.5 c.c. for each millimeter of change. From this volume was deducted the air displaced by the subject, which was taken as the equivalent in liters of his body-weight. The corrected volume was then reduced to 0° C. and 760 mm. of pressure. The percentage of carbon dioxide as found by analysis and the corrected volume of the air in the chamber gave the total volume of carbon dioxide present at the start; a similar calculation gave the volume of carbon dioxide present at the end and the difference between the amounts, divided by the time elapsed, gave the carbon dioxide produced per minute.

The calculation of the oxygen consumed was not so simple, because, as stated elsewhere, the time available for each subject was limited to approximately 45 minutes, which precluded a determination with the Sonden gas-analysis apparatus of the oxygen present at both the beginning and end of the experiment. The oxygen present in the chamber at the start was obtained by computation as follows:

It was assumed that the respiratory quotients of the normal subjects would be approximately 0.85; those of the men on the restricted diet were found to be more nearly 0.81. It was also assumed that the air in the chamber before the cover was lowered was practically of the same composition as outdoor air, this being due to the open windows and complete ventilation of the chamber and room. The percentage of oxygen consumed from the chamber during this preliminary period would therefore be in the following ratio:

Per cent C02 found: per cent O2 consumed:: R. Q.: 1 Deducting this calculated percentage of oxygen consumed from the percentage of oxygen in outdoor air would give the percentage of oxygen present in the chamber at the beginning of the period, subject to a correction for change in the volume of air in the chamber due to the fact that more oxygen has been consumed than carbon dioxide has been produced. Of the original air 100 volumes were composed as follows: 02, 20.932;1 C02, 0.031; N2, 79.037; total, 100.000. The altered volume is composed of 79.037 parts of unchanged nitrogen plus an increased amount of carbon dioxide, and a decreased amount of oxygen, the total being less than 100. The true percentage of oxygen would therefore be larger in the proportion as the altered volume is to 100. From this corrected percentage and the volume of air in the chamber, the amount of oxygen present at the start is computed. The analysis of the air by the Sonden gas-analysis apparatus at the end of the experiment gave the combined percentage of oxygen and carbon dioxide, from which the percentage of oxygen was found by deducting the percentage of carbon dioxide as determined simultaneously on the two Haldane gas-analysis apparatus. The difference between the volume of oxygen present at the start and at the end, divided by the time, gave the oxygen consumed per minute. The data and calculations of a typical experiment are shown in tables 6 and 7.

Table 6. - Records Of Metabolism Experiment, With Subject Walking In Treadmill Chamber

Subject: Gul. Date, Feb. 3, 1918. Weight with clothes, 64 kg. Experiment began 7h18m a. m.

1Benedict, Carnegie Inst. Wash. Pub. No. 166, 1912, p. 114.

Table 7. - Calculation Of Metabolism Experiment With Gul Walking In Treadmill Chamber Feb. 3, 1918

Calculation of Carbon Dioxide Produced.

(A) Carbon Dioxide Present At Start Of Period

(B) Carbon Dioxide Present At End Of Period

Duration of period, 20 minutes. CO2 produced per minute, 614 c.c.

Calculation Of Oxygen Consumed. (A) Oxygen Present At Start Of Period

100 volumes of the air originally in the chamber, assumed to be of outdoor composition, would consist of 20.032 volumes O2; 0.031 volume CO2; and 79.037 volumes N2; total, 100.000 volumes; but since then has been a diminution in the volume in the chamber due to the fact that more oxygen has been consumed than carbon dioxide has been formed, and since the volume of nitrogen is unchanged, it is evident that at the start of the period these 100 volumes are altered to the following: N2 (unchanged), 79.037 volumes; CO, (by analysis), 0.143 volume; O2 (by computation above), 20.792 volumes; total, 99.972 volumes, of which the percentage of oxygen would be 20.792/99.972 X100 = 20.798.

1 Observed barometer minus corrections for barometer temperature (brass scale) and aqueous tension. 2 The oxygen in the air on a CO2-free basis - 20.938 per cent; carbon dioxide = 0.031 per cent.

(Benedict. Carnegie Inst. Wash. Pub. No. 166, 1912, p. 114).

The correct percentage of oxygen at the start is therefore 20.798. Volume of chamber at 0°, 760 mm. at start was 2,175.8 liters.

(B) Oxygen Present At End Of Period

Duration, 20 minutes.

Oxygen consumed per minute, 665 c.c.

Respiratory quotient, CO2/O2 = 614/665 = 0.92.

1,000 c.c. CO, at respiratory quotient of 0.92-5.378 cals.;1 e. g., 614 c.c. =3.30 cals.