THE BLOODVESSELS 



77 



is a reflection from the aortic valves, is shown by the tracing 

 in Fig. 31, taken from the facial artery of the horse, A before, 

 and B after destruction of the valves. In B the dicrotic wave 

 has disappeared. A well-marked dicrotic pulse gives a double 



J I u 



Fig. 31. — Tracing from the Facial Artery of the Horse (Hamilton). 

 A , before, B after destruction of the aortic valves. 



beat of the pulse for each single contraction of the heart (see 

 Figs. 32 and 33). Venous pulse tracings are referred to 

 at p. 44. 



The pulse-wave distends all the arteries of a part, and by so 

 doing actually increases the volume of the organ at the moment 

 of its passage ; this has been described as the volume pulse, 

 and it can be recorded in the following manner : A limb, a kidney, 

 or spleen, is placed in a closed chamber containing fluid ; at 

 each passage of the pulse- wave the volume of the part, being 

 increased, causes an increased pressure in the fluid, and this, bv 





Fig. 32. — Pulse Tracings (Stewart). 



1, Primary elevation ; 2, predicrotic or first tidal wave ; 3, dicrotic wave. The 

 depression between 2 and 3 is the dicrotic or aortic notch ; 3 is better marked 

 in B than in A. C, dicrotic pulse, with low arterial tension ; D, pulse with 

 high arterial pressure, summit of primary elevation in the form of an 

 ascending plateau. 



means of any of the methods of registering changes of pressure 

 in a fluid, may be made to furnish a graphic record. Such an 

 instrument is known as a plethy sinograph, and in Fig. 34 the 

 apparatus may be seen as applied to the arm. So sensitive 

 may this method of registration be made, that a tracing of 



