P U L 8 E - T R A C I N G S. 



125 



It is evident that the beating of the pulse with the reaction 

 of the spring will cause an up-and-down movement of the 

 lever, and if the extremity of the latter be inked, it will write 



FIG. 42. 



Diagram of the mode of action of thesphygmograph. 



the effect on the card, which is made to move by clockwork in 

 the direction of the arrow. Thus a tracing of the pulse is ob- 

 tained, and in this way much more delicate effects can be seen, 

 than can be felt on the application of the finger. 



FIG. 43. 



The sphygmograph applied to the arm. 



Fig. 44 represents a healthy pulse-tracing of the radial 

 artery, but somewhat deficient in tone. On examination, we 

 see that the up-stroke which represents the beat of the pulse 

 is a nearly vertical line, while the down-stroke is very slanting, 

 and interrupted by a slight reascent. The more vigorous the 

 pulse, if it be healthy, the less is this reasceut, and vice versd. 

 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 therefore less interrupted. 



Sometimes the up-stroke has a double apex, as in Fig. 46. 

 This will be explained hereafter. 



11 



