EXPERIMENTS WITH HORIZONTAL WALKING. 171 



by the increase in the pulse-rate and its attendant blood-flow if that 

 factor were known, while a ventilation of 14 liters per minute was 

 sufficient to meet the needs during this range of increasing work. 

 The high oxygen consumption of 633 c. c. at 3,840 h. kg. m. referred to 

 in the previous paragraph is accompanied by an increase in pulse- 

 rate, but no change is evident in the ventilation at this time. 

 Beyond 4,292 h. kg. m. the ventilation curve shows a marked increase, 

 while the increase in the pulse is less in degree, indicating that here 

 the demand for oxygen was not met by an increase in the pulse so 

 much as by a larger pulmonary ventilation. The respiration-rate and 

 the volume per inspiration determine the pulmonary ventilation. 

 A reference to the curve for the respiration-rate shows that up to 4,292 

 h. kg. m. the increase in the pulmonary ventilation must come from an 

 increase in volume per inspiration rather than from any increase in the 

 respiration-rate. Beyond 4,292 h. kg. m. the respiration-rate shows a 

 sharp increase in keeping with the ventilation. With the data in hand, 

 we are not able to discuss that portion of the compensation due to an 

 increase in the oxygen-carrying power of the blood which is caused by 

 an increase in volume of the heart-output. It is evident, however, 

 that in a change from standing to walking there is possible an actual 

 decrease in pulse-rate with a simultaneous increase of 100 or more per 

 cent in the oxygen consumption. This physiological fact, even though 

 incompletely explained at this time, yet suggests many topics for 

 experimentation . 



The curves for the same factors for W. K. are also given in figure 13, 

 and though the range in the amount of work is much less, the same 

 characteristics are shown by his curves, namely, for the amount of 

 work done, that the oxygen consumption and heat-output run uniformly 

 with the increase in the horizontal kilogrammeters of work, that the 

 ventilation shows no increase for these moderate demands, but that the 

 increase in the pulse-rate is responsible for the increase in the oxygen- 

 supply. The respiration-rate for W. K., in contrast to that of E. D. B., 

 shows an increase with a constant ventilation, indicating a change to a 

 smaller volume per inspiration. 



