180 METABOLISM DURING WALKING. 



series was duplicated under the same conditions. Considering average 

 values only, it can be seen that the carbon dioxide on the first day was 

 slightly larger when the mouthpiece was inserted 15 minutes before the 

 test, but on the second day it was practically the same with both periods 

 of preliminary breathing. The oxygen consumption was somewhat 

 higher on the first day and correspondingly lower on the second day 

 with the long preliminary breathing. The respiratory quotient was 

 slightly higher in both series of tests with the longer preliminary 

 breathing. The evidence as a whole can not be said, however, to 

 indicate that with this subject standing there is an appreciable differ- 

 ence in the effect upon the measured metabolism as to whether the 

 mouthpiece is inserted 15 minutes before the period begins or imme- 

 diately before. 



On four days walking experiments were made, and while there was 

 every effort to secure exactly the same rate of walking, unfortunately 

 this could not be maintained. Slight differences in the total amount of 

 work performed accordingly appear. While the rate of walking was 

 approximately 50 meters per minute, a little less than 2 miles an hour, 

 it actually varied in the different periods on these days from 47.2 to 

 53.0 meters per minute. Usually the rate of walking was slightly 

 greater with the second test in the comparison, namely, that with the 

 short preliminary breathing, the difference averaging not far from 

 1 per cent. These differences are important to take into consideration 

 in the analysis of the results. 



Of the two factors, carbon dioxide and oxygen, one would naturally 

 expect that an abnormality in respiration due to the mouthpiece would 

 produce more immediate fluctuations in the amount of carbon dioxide 

 exhaled. This may be owing to a local "pumping-out" effect, and 

 consequently it is not surprising that the values for carbon dioxide do 

 not show regularity. On the first two days with grade walking these 

 values are somewhat higher, and on the last two days measurably lower 

 with the short preliminary breathing period. Since, as stated above, 

 when there was a difference in the rate of walking, it was almost 

 invariably more rapid in the second test of the comparison, it can be 

 seen that there is no relationship between the carbon dioxide and the 

 slightly higher rate of walking, nor indeed any relationship with the use 

 of the mouthpiece, and the differences in amounts simply illustrate the 

 variability in the carbon-dioxide excretion that one may expect to 

 find under the conditions of a test liks this. 



A truer measure of the metabolism is the oxygen consumption, and 

 we find here that on all four days the oxygen consumption was slightly 

 higher in the period with the short preliminary breathing. This is 

 almost always in full accord with the slight differences in the rate of 

 walking, and can therefore be readily explained by an increase in the 

 oxygen consumption necessitated by an increase in the rate of walking. 



