RESPIRATION 



263 



much as six times as great as during rest. As the pulse rate only 

 went up to about double the normal, the volume of blood expelled 

 from the heart at each systole must, if these results were reliable, 

 have been trebled. This would be just as striking an increase as 

 occurs in the depth of breathing during muscular work. The values 

 for utilization of the available oxygen of the arterial blood are 



not very far from those obtained in the horse by Zuntz and 

 Hagemann, but do not agree at all well with those of Loewy and 

 von Schrotter in man. In the case of six experiments on different 

 individuals where approximate data were available the latter 

 observers calculated a utilization of rather less than 20 per cent 

 during rest. 



During or since the war several other observers have used the 

 method of Krogh and Lindhard, and obtained more or less similar 

 results. These observers include Boothby,^^ as well as Newburgh 

 and Means^^ in America. Lindhard^^ has also published a 

 number of additional results, which give, on the whole, a distinctly 

 higher rate of circulation, and lower percentage utilization of 

 oxygen, during rest. 



The subject had meanwhile been approached by a quite different 

 method by Yandell Henderson.^ He used dogs for his experi- 

 ments, and placed a recording plethysmograph round the heart 

 after removing the pericardium. By this method he found that 

 the volume of blood discharged per heartbeat was approximately 

 the same, whether the heart was beating faster or slower. Thus 

 within wide limits the volume of blood discharged per minute 



'^Boothby, Amer. Journ. of Physiol., XXXVIll, p. 383, 1915. 



'^ Newburgh and Means, Journ. of Pharm. and Exp. Therap., VII, p. 4, 19 15. 



"^ Lindhard, PfHiger's Archiv. 



* Yandell Henderson, Amer. Journ. of P/tysioL, XVI, p. 325, 1906. 



