255 



The Resonance of the Tissues as a Factor in the Transmission of 



the Pulse and in Blood Pressure. 

 By Leonard Hill, M.B., F.R.S., James M. McQueen, M.A., B.Sc, M.B., 



(From the Physiological Laboratory, London Hospital, and the Pathological Laboratory, 



Aberdeen University.) 



Systolic blood pressure in man is measured by the pressure indicated on a 

 manometer scale at the point of disappearance and reappearance of the pulse. 

 When the pressure is raised in the armlet of the Biva-Rocci or Hill-Barnard, 

 or their modifications, or in the bag of the pocket sphygmometer (L. Hill), the 

 pulse is supposed to disappear at the moment when the arterial lumen is 

 obliterated, and to reappear when the patency of the channel is re-established. 

 Consequently every effort has been made to secure that the pressure should 

 be transmitted to the arterial wall as far as possible without loss. Accuracy 

 in instrumental readings has been held to be conditional on such perfect 

 transmission of pressure. 



Of late years controversy has ranged round the importance of the arterial 

 wall as a factor in blood pressure, especially in diseased conditions of the 

 wall, e.g. arteriosclerosis. One of us (L. Hill) with Russell Wells (2) and 

 Martin Flack (3) has shown the importance of the arterial wall in influencing 

 conduction of the pulse, and has ascribed the high readings obtained in the 

 arteries of the leg in cases of aortic regurgitation to a better conduction of 

 the pulse in contracted and more rigid arteries. There remains for us in 

 this paper to demonstrate another factor, hitherto overlooked, in the taking 

 of blood-pressure observations, namely, the influence on the arterial pulse 

 of the resonance of the tissues permeated with arterioles. The pulse is 

 essentially a phenomenon of periodic vibrations, and by the resonance of the 

 tissues we denote the property of the tissues to further the pulse vibrations 

 by synchronous vibrations of like (positive) periodicity. 



Our observations have been made in the first place on a man, a boiler- 

 maker by trade, aged 53 years, whose arteries show on both arms slight 

 though equal arteriosclerosis. His apex beat is visible within the nipple 

 line, and his cardiac valves are intact. No aneurismal condition is detected. 



His right radial artery pursues an aberrant course, curving some 3 inches 

 above the styloid process of the radius over the supinator longus muscle on 

 to the dorsal surface of the forearm, where it runs over the extensor tendons 



vol. lxxxvii. — b, s^^M-->' 



and William W. Ingram, M.B., Ch.B. 



(Received June 24 — Read June 26, 1913.) 



