118 METABOLISM DURING WALKING. 



age speed was very considerable, i. e., from 35.8 to 97.4 meters per 

 minute. Since the extreme speeds at which E. D. B. walked were not 

 natural, but forced, an average value has therefore but little signifi- 

 cance. For comparison with the results obtained with other subjects, 

 an average has been found for these days when the speed of walking 

 fell within the ranges of 55 to 65 meters per minute. This shows a 

 total average oxygen consumption per minute of 607 c. c. and a heat- 

 output of 2.94 calories. 



Considering the large number of determined respiratory quotients 

 of E. D. B., it will be found that the quotient of the first period of the 

 day is usually higher than that of subsequent periods and that the 

 difference between the first and second periods is usually greater than 

 that between the second and succeeding periods. This is apparently 

 due to both the carbon dioxide and oxygen, for, in general, it may be 

 noted that the elimination of the carbon dioxide decreased and the 

 oxygen consumption increased in the second period. Since the periods 

 were preceded by several minutes of preliminary walking, any tendency 

 toward an unnatural ventilation of the lungs would probably have 

 been eliminated before the period began. Furthermore, any change 

 in volume of the ventilating system due to the warmth and moisture of 

 the exhaled air would probably have been overcome by the time the 

 final admission of oxygen was made. Such small increase as there was 

 in the temperature of the soda-lime and sulphuric acid in the absorbers 

 would therefore be practically alike in all periods and the effect would 

 be to decrease the oxygen admitted to the system rather than to in- 

 crease it. It would seem from a study of the respiratory quotient in 

 this connection that there was a gradual change in the character of the 

 material oxidized in the body. If this is not the case, and if the change 

 in the oxygen consumption and respiratory quotient is in fact due to 

 some fixed error in the technique, the heat-output as calculated for the 

 first period is too high. Since the heat-output used, however, is 

 ordinarily the average of from three to five periods, any error due to 

 this cause has no significance in the general picture. 



Of the three remaining subjects (see table 12, p. 68), the only special 

 features to be noted in the results are that the heat-output for J. H. G. 

 was the largest on his first day, also that his respiratory quotients are 

 lower than those of the subjects previously discussed. The highest 

 heat-output for E. L. F. was on his first day, although the rates of 

 walking were fairly uniform for all three days. H. M. S. shows a low 

 respiratory quotient, which is in keeping with the low respiratory 

 quotients found in his standing experiments. 



The average total metabolism for these men, walking at what may 

 be called natural speeds, is shown in table 28. From this table it is 

 seen that the heat-output per kilogram of body-weight per hour for the 

 more natural speeds lying between 50 and 80 meters per minute ranged 



