i 5 8 



THE CIRCULATION. 



spring, which allows the lever to move up, at the same 

 time that it is just strong enough to resist its making any 

 sudden jerk, and in the interval of the beats also to assist 

 in bringing it back to its original position. For ordinary 

 purposes, the instrument is bound on the wrist (Fig. 43). 

 Fig. 42. 



It is evident that the beating of the pulse with the 

 reaction of the spring will cause an up-and-down move- 

 ment of the lever, and if the extremity of the latter be 

 inked, it will write 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 obtained, and in this way much 

 more delicate effects can be seen, than can be felt on the 

 application of the finger. 



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

 artery, but somewhat deficient in tone. On examination, 

 we see that the upstroke which represents the beat of the 

 pulse is a nearly vertical line, while the down-stroke is 

 very slanting, and interrupted by a slight re-ascent. The 

 more vigorous the pulse, if it be healthy, the less is this 



