THE PULSE. 



179 



129. We have now to study the nature and characters of the pulse in 

 greater detail. 



We may say at once, and indeed have already incidentally seen, that 

 pulse is essentially due to the action of physical causes ; it is the 



the 



FIG. 62. 



Pulse Tracing from the Radial Artery of Man The vertical curved line L, gives the tracing 

 which the recording lever made when the blackened paper was motionless. The curved inter- 

 rupted lines show the distance from one another in time of the chief phases of the pulse-wave, 

 viz., x = commencement and A end of expansion of artery; p, pre-dicrotic notch, d, dicrotic 

 notch. C, dicrotic crest. D, Post- dicrotic crest. /, the post-dicrotic notch. These are explained 

 in the text later on. 



physical result of the sudden injection of the contents of the ventricle into 

 the elastic tubes called arteries; its more important features may be ex- 



[FiG. 63. 



Apparatus of Marey for showing Mode in which Pulse is Propagated in the Arteries: B is a 

 rubber pump, with valve attachment, to prevent a regurgitant current; I, V , I", are levers resting 

 on a gum tube, at intervals of 20 cm. of tubing; C, drum upon which tracing is made ; H, clock- 

 work to revolve drum.] 



plained on physical principles and may be illustrated by means of an arti- 

 ficial model [Fig. 63]. 



If two or more levers be placed on the arterial tubes of an artificial 

 model, Fig. 63, one near to the pump, and the others equal distances apart, 

 with a considerable length of tubing between the proximal and distal levers, 

 and the levers be made to write, on a vertical line, on a recording surface, 



