114 VELOCITY OF THE PULSE-WAVE IX MAN. 



A, with 18 cm. (Hg.) pressure, the velocity per metre = 0-093 second, while with 21 cm. pres- 

 sure (Hg.) = 0'095 second per metre. 



(C) The specific gravity of the liquid influences the velocity of the pulse-wave. In mercury 

 the wave is propagated four times more slowly than in water. 



(D) The velocity in a tube which is more rigid and not so extensile is greater than in a tube 

 which is easily distended. 



78- VELOCITY OF THE PULSE-WAVE IN MAN. Landois obtained the following results 

 in a student : Difference between carotid and radial = '074 second (the distance being taken 

 as 62 centimetres) ; carotid and femoral = '068 second ; femoral (inguinal region) and posterior 

 tibial = 0*097 second (distance estimated at 91 centimetres). [Waller obtained between the 

 heart and carotid 0'10 second : heart and femoral, 0*18 sec. ; heart and dorsalis pedis, 0*22.] 



The velocity of the pulse-wave in the arteries of the upper extremities = 8 -43 

 metres per second, and in those of the lower extremity 9'40 metres per second, [i.e., 

 about 30 feet per second]. The velocity is greater in the less extensile arteries of 

 the lower extremities than in those of the upper limb. For the same reason it is 

 less in the peripheral arteries and in the yielding arteries of children (Czermak). 



E. H. Weber estimated the velocity at 9*24 metres per second; Garrod, 9-10 - 8 metres; 

 Grashey, 8*5 metres ; Moens, 8 '3 metres, and with diminished pressure during Valsalva's experi- 

 ment 7 -3 metres ( 60, 74). 



Influencing Conditions. In animals, haemorrhage, slowing of the heart produced by stimula- 

 tion of the vagus (Moens), section of the spinal cord, deep morphia-narcosis, and dilatation of 

 the blood-vessels by heat, produce slowing of the velocity, while stimulation of the spinal cord 

 iica U rati s it (Grunmach). 



The wave-length of the pulse-wave is obtained by multiplying the duration of 

 the inflow of blood into the aorta = O0& to 0*09 second ( 51), by the velocity of 

 the pulse-wave. 



Method. Place the knobs of two tambours (fig. 76) upon the two arteries to be investigated, 

 or place one over the apex-beat and the other upon an artery. These receiving tambours are 

 connected with two registering tambours, as in Brondgeest's pansphygmograph ( 67, fig. 76), 

 so that their writing-levers are directly over each other, and so arranged as to write simultane- 

 ously on one vibrating plate attached to a tuning-fork. [Or they may be made to write upon a 

 revolving cylinder, whose rate of movement is ascertained by causing a tuning-fork of a known 



rate of vibration to write under them.] The apparatus is 

 improved by using rigid tubes and filling them with water, 

 in which all impulses are rapidly communicated. In arteries 

 which are distant from each other, or in the case of the heart 

 and an artery, the two knobs of the receiving tambours may 



Fig. 96. 

 A, curve of radial artery on a vibrating surface (1 vib. =0*01613 sec.) ; P, apex of curve ; e, e,. 

 elastic vibrations ; 1{, dicrotic wave. B, curve of same radial taken along with the heart- 

 beat ; r, H, P, contraction of the ventricle. 



be connected by means of a Y-tube with one writing-lever. In fig. 96, B is a curve from the 

 radial artery taken in this way. In it v H P indicates contraction of the ventricle ; H, the 

 apex of the ventricular contraction; P, the primary apex of the radial curve; v, the beginning 

 of the ventricular contraction ; p, of the radial pulse. A is the curve of the radial artery alone. 

 From these curves it is evident that in this instance nine vibrations occur between the begin- 

 ning of the ventricular contraction and the beginning of the pulse in the radial artery = 

 0'15 sec. 



In rig. 97 the difference between the carotid and the posterior tibial pulse = 0*137 sec. 



Pathological. In cases of diminished extensibility of the arteries, e.g., in atheroma ( 77, D), 

 the pulse-wave is propagated more rapidly. Local dilatations of the arteries, as in aneurisms, 

 cause a retardation of the wave, and a similar result arises from local constrictions. Relaxation 

 of the walls of the vessels in high fever retards the movement (Hamernjk). 



79 OTHEE PULSATILE PHENOMENA. 1. In the mouth and nose, when they are filled 

 with air, and the glottis closed, pulsatile phenomena (due to the arteries in their soft parts), 



