228 METABOLISM DURING WALKING. 



it may be seen that the curve for the 35 per cent grade lies above 

 that for the 30 per cent grade instead of slightly below it. This 

 reverse in relationship is also found for the lowest point on the 25 per 

 cent curve and for the two points for the 45 per cent grade, but these 

 exceptions do not give sufficient cause for questioning the other curves, 

 since the carbon-dioxide and oxygen curves for both subjects indicate 

 that a definite amount of work can be performed at an optimum by 

 intensifying the grade and lowering the speed. The general picture of 

 these curves for both carbon dioxide and oxygen is that the relationship 

 between the rate of increase in the metabolism and in the work per- 

 formed is uniform within the ranges here reported. 



The curves for the oxygen consumption of W. K. and E. D. B. in 

 relation to the kilogrammeters of work are also presented in figures 23 

 and 24 (pp. 236 and 237), as plotted from the averages given in table 56, 

 in which the data are grouped according to grade and speed. 1 



The curve for W. K. (fig. 23) indicates a slight change in trend in the 

 region of 200 kg. m., but that of E. D. B. (fig. 24) is linear throughout 

 the entire length. From the course of the curve for E. D. B., 425 c. c. 

 per minute would appear to be the requirement for maintenance, hori- 

 zontal increment, step-lift, etc., upon which the requirement for grade 

 work per se is superimposed. The slope of the curve shows that on the 

 average each kilogrammeter of grade work required an oxygen con- 

 sumption of 1.7 c. c. throughout the range of E. D. B.'s endurance. 

 The break in the curve for W. K. at 200 kg. m. makes an estimate of 

 his requirements uncertain, but above 300 kg. m. his curve is linear, 

 and from the slope of this part of the curve it would appear that the 

 oxygen consumption was 1.95 c. c. for each kilogrammeter of work in 

 the range studied, i. e., between 100 and 900 kg. m. 



From the curves in figures 23 and 24 an estimate has been made for 

 both W. K. and E. D. B. of the average oxygen consumption for in- 

 creasing amounts of work performed. These figures are recorded in 

 the second column of tables 58 and 59. The total and percentage 

 increases over the standing requirement are likewise given. These 

 tables show that, in the range covered, the increase in the total amount 

 of oxygen consumed and both the total and the percentage increases 

 over the standing requirement were larger for W. K. than for E. D. B. 

 Thus, for 900 kg. m. (the maximum amount of work done by W. K.), 

 the total oxygen consumption over the standing requirement was 1,982 

 c. c., or 869 per cent above the standing value for W. K., while for 

 E. D. B. for an equal amount ol work, the corresponding values were 

 1,740 c. c. of oxygen and 725 per cent above the standing requirement. 

 It is also seen from these tables that it cost more per unit of 100 kg. m. 



lr The curves sketched through the points in these figures and also those in figures 28 and 29 

 for respiration-rate, pulmonary ventilation, and pulse-rate, represent the average of estimates 

 made by three members of the Laboratory staff. 



