102 



THE MECHANISM OF THE CIRCULATION. 



The velocity of the pulse wave. — The fact that the carotid pulse 

 is earlier in time than the radial pulse is determinable by the fingers of 

 a practised observer. AVith the help of a clock beating thirds of a 

 second, E. H. Weber 3 found the difference time between the perception 

 of the pulse in the maxillary and anterior tibial artery to be respectively 

 \ to \ second. From this result the velocity of transmission was calcu- 

 lated to be 7'92 to 9*24 metres per second. 



Later observers have obtained, by means of tambours, synchronous 

 graphic records from two different arteries. Some selected examples of the 

 results obtained by different workers are given in the following table : 4 — 



The variations in the rate of transmission depend on the elastic 

 coefficient of the arterial wall. With a rise of arterial pressure the 



1 Nagele found in six hundred observations the extremes to be 90 and ] 80, the average 135, 

 "Die geburtshulfliehe Auscultation," Mainz, 1838, S. 35. 



2 Milne -Ed wards, loc. cit., p. 57. 



3 " Annotationes anatomicse et physiologicae," Leipzig, 1834, Bd. i. ; Btr. d. k. Sachs. 

 Gesellsch. d. Wissensch., math.-phys. CI., Leipzig, 1850, S. 196. 



4 After Tigerstedt, "Physiol, des Kreislaufes," 1894, S. 385. 

 8 "Die Lehre vom Arterienpuls," Berlin, 1872, S. 297. 



6 " Sphygmography and Cardiography," New York, 1887, p. 41. 



7 Skandin. Arch. f. Physiol, Leipzig, 1889, Bd. i. S. 96. 



8 Arch./, d. gcs. Physiol., Bonn, 1889, Bd. xlvi. S. 132. 



