344 Messrs. Hill, McQueen, and Flack. Conduction of the 



Table VIII. 



Source of Mature 

 Rats (over 90 grm.). 



Source of Immature 

 Rats (90 grms. or less). 



Coefficient of 

 Correlation.* 



March data 

 April „ 

 May „ 

 April „ 

 March „ 

 March „ 



March data 

 April „ 

 May „ 

 May „ 

 May 



April „ 



-0-23±0-04 

 -0 70±0 02 

 -0-81 ±0-01 

 -0-76±0-02 

 -0-69±0-02 

 -0-62±0-02 



* The coefficients were determined by means of Pearson's approximate method ( ' Phil. Trans.,' 

 A, vol. 195, p. 16, equation lvii) and the probable error assumed to be 3[0 • 67449 (l — r 2 )/</n~\. 



The Conduction of the Pulse Wave and the Measurement of 



Arterial Pressure. 

 By Leonard Hill, F.R.S., James McQueen, and Martin Flack* 



(Received December 20, 1913, — Read February 5, 1914.) 



(From the Physiological Laboratory, London Hospital Medical College, London Hospital 

 Besearch Fund ; and the Pathological Laboratory, Aberdeen University.) 



It is now well established that in cases of aortic regurgitation placed 

 in the horizontal position the arterial pressure is considerably higher 

 (50-80 mm. Hg) in the leg than in the arm.f Such pressures are taken by 

 the sphygmomanometer, using the armlet method, the armlet being placed 

 respectively round the calf and the upper arm, the disappearance and 

 reappearance of the pulse wave being noted in the dorsalis pedis or posterior 

 tibial artery, and in the radial. 



In seeking for an explanation of this phenomenon it has already been 

 suggested by us} that the " lability " of the arterial wall plays a considerable 

 part, the term " lability " being used to designate the ease with which an 

 artery distends with a rise and recoils with a fall of arterial pressure. The 

 effect of increased and of diminished lability of the vessel wall upon the 

 conduction of the pulse wave has been demonstrated schematically by 



* During tenure of Eliza Ann Alston Research Scholarship. 



t Hill, Flack, and Holtzmann, ' Heart,' vol. 1, p. 73 (1909) ; also Hill and Rowlands, 

 ' Heart,' vol. 3, p. 222 (1912). 



1 Hill and Flack, ' Roy. Soc. Proc.,' B, vol. 86, p. 365. 



