298 



Messrs. J. C. Bramwell and A. V. Hill. 



(13) Tigerstedt, C, " Zur Kenntnis der von dem linken Herzen herausgetriebenen 



Blutmenge in ihrer Abhangigkeit von verschiedenen Variabeln," 'Skand. Archv. 

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(14) Tigerstedt, B., " Neue TJntersuchungen liber die von dem linken Herzen heraus- 



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(15) Tucker, W. S., and Paris, E. T, "A Selective Hot-Wire Microphone," 'Phil. 



Trans.,' A, vol. 221, pp. 389-430. 



The Velocity of the Pulse Wave in Man. 

 By J. Ceighton Beamwell* M.B., M.E.C.P., and A. V. Hill, F.R.S. 



(Received February 4, 1922.) 



In an investigation now being carried out by us at Manchester observa- 

 tions are being made, under various conditions, upon the velocity of the pulse 

 wave in man. As a preliminary to this investigation it was thought advisable 

 to stud)'' the theory of the transmission of the pulse wave, and the following 

 pages contain the results arrived at, together with an account of experiments 

 upon the velocity of the pulse wave in an isolated human artery. 



The pulse wave in man travels in the arteries at a speed of 4 to 10 metres 

 per second. Its velocity depends, to a small degree, on the velocity of the 

 blood in the artery considered, but chiefly upon the elastic condition of the 

 arterial wall, which is affected by a variety of factors in health and disease. 

 As regards the former, the pulse wave must be considered as travelling, like 

 a ripple on nidving water, relatively to the fluid in which it occurs. The 

 arterial wall merely exerts an elastic constraint upon the surface of the fluid, 

 and in the simplified theory of the transmission of the wave (which it is 

 necessary for practical purposes to adopt) the inertia of the wall, and of the 

 tissues outside it. exerts no influence on the velocity of the wave. Thus any 

 experimentally determined value must represent the velocity of the wave 

 relatively to the blood, plus the velocity of the blood in the artery. Taking 

 0'75 metres per second as an average maximum velocity of the blood in the 

 aorta, and 025 metres per second as an average maximum in the carotid 

 artery (4), we see that the correction for the velocity of the blood itself is small, 

 but not negligible, in comparison with the velocity of the wave. Any con- 

 siderable increase in the velocity of the blood, caused, e.g., by local or general 

 exertion, will cause an equal increase in the velocity of the pulse wave. 



* Working for the Medical Besearch Council. 



