RESPIRATION 269 



great. Roughly speaking, therefore, our results confirm those 

 obtained by Henderson on the dog. 



Henderson and Prince have determined in a number of persons 

 the oxygen consumption per beat of the heart, or what they call 

 for brevity "the oxygen pulse." 8 This value is obtained by simply 

 dividing the oxygen consumption per minute by the pulse rate. 

 Figure 69 shows graphically a fairly typical example of their 



g 



25 25oo 



20 2000 



15 '500 



JO 'Ooo 



5 500 



Pulse 60 70 &o 90 100 no 120 130 140 150 160 



Figure 69. 



Subject Y. H., Weight 75 kilos. Haemoglobin 107. In this diagram the 

 broken line expresses the oxygen consumption per minute, the dotted line the 

 CO 2 elimination, and the solid line the oxygen pulse. During the short periods 

 of vigorous exertion and rapid heart rates, the CO2 elimination was increased 

 to a greater extent than the oxygen consumption, the respiratory quotient even 

 rising above unity in some cases, and indicating an excessive blowing off 

 of C0 2 . 



results. It will be seen that with low oxygen consumption per 

 minute the oxygen consumption per beat is low, but increases 

 rapidly up to a maximum as the oxygen consumption per minute 

 increases owing to muscular exertion. When, however, this maxi- 

 mum is reached, further increase of the oxygen consumption per 

 minute causes no increase in the oxygen consumption per beat. 

 Interpreting these data in the light of our own experiments on 

 man, and Henderson's former experiments on the heart of the dog, 

 the increased oxygen consumption per beat is not due to any 

 marked extent to increased output of blood per beat, but to in- 

 creased utilization of the charge of oxygen in the arterial blood. 



8 Yandell Henderson and Prince, Amer. Journ. of Physiol., XXXV, p. 106, 1914. 



