178 METABOLISM DURING WALKING. 



tion especially large. Is the resistance, for example, too great? Of 

 special interest is the fact that much of this report deals with the 

 physiology of respiration during the period of transition from standing 

 to walking, and the reverse from walking to standing. If breathing 

 through a mouthpiece is abnormal, the value of these studies of transi- 

 tion would be lessened. 



In the ordinary technique the mouthpiece is usually inserted about 

 two minutes before the actual experiment begins. To test the question 

 as to whether this preliminary period of breathing through the mouth- 

 piece was sufficiently long for the subject to adjust himself to the new 

 conditions, a number of experiments were carried out in which the 

 mouthpiece was inserted 15 or more minutes before the actual beginning 

 of the experiment, and a comparison series of experiments was made 

 in which the mouthpiece was inserted almost immediately, i. e., a few 

 seconds before the period began. These experiments were all with 

 E. D. B. between March 2 and 8, 1916, inclusive. On two of the days 

 the subject stood; on four of the days he walked on a 30 per cent incline 

 at a rate of approximately 50 meters per minute. The standing or 

 walking was continuous on every day throughout each set of two com- 

 parison periods, and at the end the subject sat down and rested. In 

 the first period in each pair the subject breathed through the mouth- 

 piece on an average of 15 minutes before the period began. The actual 

 period for the measurement of the metabolism varied from 7 minutes 

 and 24 seconds to 10 minutes and 52 seconds, averaging not far from 

 9 minutes. There was then an interval which was usually 10 to 12 

 minutes long. On March 4 the first interval was 20 minutes and on 

 March 7 the interval, owing to some trouble with the apparatus, was 

 50 minutes. On both these days walking experiments were made, and 

 the subject walked continuously even in these intervals. 



In the second period in the comparison the mouthpiece was not in- 

 serted until just before the beginning of the test, so that usually the 

 period began on the second respiration, with an interval between the 

 insertion of the mouthpiece and the beginning of the metabolism 

 measurements of never more than 15 seconds. Since this procedure 

 was carried out in both the standing and walking comparisons, it 

 would seem as if the influence of mouthpiece breathing upon the metab- 

 olism and physiological factors should be demonstrated by such a 

 series of tests. 



EFFECT OF MOUTHPIECE BREATHING UPON METABOLISM. 



Although the data for these comparison tests are incorporated in the 

 statistical tables 6 and 16, they are also summarized here in table 49. 

 In the first test, namely, March 2, 1916, the influence on the metabolism 

 of the time of insertion of the mouthpiece was studied only with the 

 subject standing, and three comparisons were made. On March 3 the 



