970 



PHYSIOLOGY 



of the sudden wave of pressure started in the aorta must be to diminish the 

 rapidity of onset of each primary wave, and therefore to diminish the 

 secondary vibrations of the curve. In an elastic system of tubes such as 

 the arterial system, there are factors at work analogous in many respects 

 to those responsible for the deformation of the curve given by an imperfect 

 manometer. These would be of two kinds viz. oscillations of the column 

 of fluid within the stretched arterial wall, and the reflection of waves from 

 different points in the periphery. Many of these reflections will interfere 

 with and annul one another. But in the arterial system there are certain 



A, 



Fi3. 427. Pulse-pressure curves taken by means of Frank's manometer (FRANK). 

 B, c, aortic pressure curves at different rates of the heart; D and E, aortic 

 pressure curve, D, compared with simultaneous record of the pressure in the femoral 

 artery E. 



points where distinct reflections of waves can be expected e. g. in the circle 

 of Willis, at the bifurcation of the aorta into the two iliac arteries, and in 

 the superficial and deep arterial arches in the hand and the foot. We have 

 distinct evidence that such waves -are set up and modify the form of the 

 pulse in the femoral and brachial arteries and their branches. Thus in 

 the Fig. 427 E, the primary rise of pressure in the femoral artery is higher 

 than even the primary rise in the aorta. This condition of ihinus is ex- 

 plicable only on the assumption of a reflected wave passing back along the. 

 artery just after the passage of the primary wave, so that the two are 

 summated. In the same way, although the dicrotic depression in the curve, 

 427 E, is no doubt mainly the propagated effect of the incisure observed in 

 the aortic pulse, it is probably deformed and the subsequent elevation 

 exaggerated as a result of reflection of the post-din otic wave from the peri- 



