EXPERIMENTS WITH HORIZONTAL WALKING. 117 



a total of 15 periods. (See table 8, p. 56.) The rate of walking varied 

 from 59.9 to 67.7 meters per minute, with an average for the six days 

 of 62.5 meters per minute. In the first experiment (March 20) there 

 was an unusually high metabolism, the oxygen consumption being 

 approximately 100 c. c. per minute more than on the next highest day, 

 and the heat-production about 0.4 calorie higher. This difference is 

 largely due to the results of the first period on this date, which possibly 

 should have been rejected. The figures have, however, been allowed 

 to stand and are used in calculating the average value. The total 

 average oxygen consumption for H. R. R. was 867 c. c. per minute, 

 with a heat-output of 4.17 calories per minute. 



With T. H. H. (fable 9, p. 57) there were seven days on which experi- 

 ments were made, with a total of 21 periods. The speed of walking 

 ranged in the individual periods only from 62.4 to 68.2 meters per 

 minute. February 25, the first day on which T. H. H. acted as sub- 

 ject, shows a much lower metabolism than that found on the other 

 days, but the fact that in two of the periods there was a marked in- 

 crease in the carbon-dioxide output with a simultaneous lowering of 

 the oxygen consumption leads one to question the normality of the 

 conditions on this day. In the experiments made from March 19 to 

 April 5, there appears to have been no marked change in the metab- 

 olism. For the seven days on which horizontal-walking experiments 

 were made with this subject, with a reasonably uniform daily speed, 

 the average oxygen intake was 678 c. c. per minute and the average 

 energy output 3.30 calories per minute. 



The results for W. K. were obtained in 16 horizontal-walking experi- 

 ments, with 52 experimental periods. (See table 10, p. 58.) The 

 majority of the experiments were made within the month of March, so 

 the picture is fairly continuous. The total heat-output had a tendency 

 to decrease somewhat as time progressed, irrespective of the fact that 

 the average speeds differed in those four weeks by a maximum of but 

 7 meters per minute from each other. The last horizontal-walking 

 experiment was made in June, three months after most of the experi- 

 ments were carried out. This day shows the lowest heat-output of 

 any of the horizontal- walking experiments with W. K., but the speed at 

 which the subject walked was also the lowest, namely, 57.1 meters per 

 minute. With this man there was an apparent tendency for the oxy- 

 gen consumption to be larger in the first periods of the day, with lower 

 values each succeeding period. The average oxygen consumption was 

 563 c. c. per minute and the average heat-output 2.72 calories per 

 minute. 



The largest number of experiments with horizontal walking was 

 made with E. D. B., these extending from October 9, 1915, to April 13, 

 1916. (See table 11, p. 60.) During this time measurements were 

 made on 61 days, with 198 periods in all. The range in the daily aver- 



