vin BLOOD-STEEAM : MOVEMENT IN VESSELS 273 



These results agree well with those of previous authors, notably 

 with those of Keyt. The differences depend principally on the 

 respective degree of elasticity of the arteries explored, and the 

 respective height of the mean blood pressure within them ; the 

 greater the elasticity of the arteries, the higher the blood pressure, 

 and the greater will be the velocity of wave transmission (Moens, 

 Grunmach, Keyt). 



Edgren's results, like the earlier conclusions of Keyt, lead us 

 to think that the velocity of the wave in the vessels is higher in 

 the upper limbs than in the lower. Edgren further found by 

 comparing the velocity of the primary and the dicrotic wave that 

 it is less in the latter. The difference, which can hardly be 

 detected between heart and radial artery, is conspicuous between 

 the heart and the femoral artery, as appears from the above tables. 



The wave-length can easily be calculated from the velocity of 

 transmission of the waves and from their number, since it is in 

 direct proportion to the rate of propagation (h) and inversely 

 proportional to the number of vibrations (n), according to the 



equation A = -. If with Edgren we reckon the time of systolic 



o'utflow = 0*23 seconds, the number of vibrations in one second will 

 be equal to 5 '75, and their velocity of propagation (taking the 

 average of that calculated by Edgren for the primary wave) is 

 equal to 6 '93 m. per second. Accordingly the wave-length 



/^,QQ 



A = v-^=l'20 m. Since in an adult the distance from heart to 

 5'75 



small arteries of the foot is a little greater, these arterial tracts of 

 the body are the only ones long enough to accommodate the entire 

 length of the pulse wave, and the end of the wave usually passes 

 the orifice of the aorta when the front of it has already reached 

 the peripheral arteries (Tigerstedt), so that these pulsate during 

 the whole of the systolic outflow. 



We know experimentally how many influences react on the 

 pulse-rate ; e.g. the lowering of blood pressure and dilatation of the 

 vessels produced by heat, by amyl nitrite, and by profound narcosis. 

 The pulse is perceptibly slowed, as can be measured not merely in 

 artificial narcosis on animals, but also in physiological sleep, and 

 on man. Patrizi compared the velocity of the pulse wave in the 

 waking state and in deep sleep, by means of experiments on a boy 

 of 13, as also the pulsations of the brain (the boy had lost part of 

 the bony substance of his cranium) and of the feet. 



Velocity of propagation in waking state, 6'50 m. per second. 

 Velocity of propagation in sleep, 5*77 in. per second. 



X. The pulsatile oscillations of pressure in the sphygmograms 

 must be distinguished from the pulsatile oscillations of velocity, 

 which are also determined by the rhythmical undulations of the 



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