FLOW OF BLOOD THROUGH THE ARTERIES 



927 



to these authors all the secondary waves on the pulse -curve are central in origin, and 

 can therefore be traced with slight modification on the curves obtained from the aorta, 

 the large and the small arteries. Although Marey investigated the propagation of 

 reflected waves and showed their presence in the artificial schema of the circulation 

 (vide p. 920), he considered that they could not contribute to the production of the 

 waves on the pulse-curve, owing to the enormous number of points at which reflection 

 might occur, so that the different reflected waves would tend mutually to annul each 

 other's effects. Moreover the distance of the dicrotic notch from the primary elevation 

 was found to be nearly the same at different parts of the system, pointing to a propaga- 

 tion of this wave from the centre to the circumference of the arterial system. 



Frank points out that the effect of the propagation of the fairly simple wave started 



E 



Fia. 417. Pulse-pressure curves taken by means of Frank's manometer (FRANK). 

 A, 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. 



in the aorta in an endless system of elastic tubes would be to diminish the rapidity 

 of onset of each vibration, and therefore to diminish the secondary vibrations on the 

 curve. In a closed elastic system of tubes, such as the arterial system, there will be 

 factors at work analogous in many respects to those responsible for the deformation 

 of the curve given by an imperfect manometer. These will be of two kinds, namely, 

 (1) oscillations of the column of fluid within the stretched arterial wall, (2) reflections 

 of waves from different points in the periphery. These reflections we should expect 

 to be evident in certain cases. Thus in the carotid there should be a reflected wave 

 from the circle of Willis ; in the descending aorta, from the bifurcation of this vessel 

 into the two iliac arteries. As a result the pulse in the peripheral .arteries, such as the 

 radial or femoral, diverges considerably from the pulse in the aorta. In the figure 

 (Fig. 417, D and E) the primary rise of pressure in the femoral artery is even higher than the 

 primary rise in the aorta, i.e. the primary wave must be augmented here by a reflected 

 wave from the periphery. Frank acknowledges that the dicrotic depression in this 

 curve is due to the propagation of the wave set up by the closure of the aortic valves ; 



