PULSE-TRACINGS. 



159 



re-ascent, and vice versa. Fig. 45 represents the tracing of 

 a healthy pulse in which the tone of the vessel is better 

 than in the last instance, and the down-stroke is there- 

 fore less interrupted. 



Sometimes the up-stroke has a double apex, as in 

 fig. 46. This will be explained hereafter. 

 Fig. 44 * 



Before proceeding to consider the formation of the pulse, 

 as shown by these tracings, it is necessary to consider what 

 are the elements combined to produce it. In the first place 

 there is a propelling organ, the heart, which at regular 

 intervals discharges a certain quantity of fluid into a tube 

 with elastic walls, filled, although not distended to the 

 utmost, with fluid. This fresh quantity of blood therefore 

 obtains entrance by the yielding of the artery's elastic 

 walls, and, on the cessation of the propelling force, the 

 blood is prevented from returning into the ventricle whence 

 it issued, by the shutting of the semilunar valves in the 

 manner before described. 



* Fig. 44. Pulse-tracing of radial artery, somewhat deficient in tone. 

 t Fig. 45. Firm and long pulse of vigorous health. 

 J Fig. 46. Pulse-tracing of radial artery, with double apex. 

 The above tracings are taken from Dr. Sanderson's work " On the 

 Sphy gmograph . ' ' 



