THE CIRCULATION OF THE BLOOD. 



canula. In response to the pressure transmitted to its interior, the 

 spring, <?, tends to straighten itself, and the movement thus produced is 



Fio. 132. 



Fio. 133. 



FIG. 132. Diagram of mercurial kymograph. A, revolving cylinder, -worked by a clockwork 

 arrangement contained in the box (B), the speed being regulated by a fan above the box; cylinder 

 supported by an upright (6), and capable of being raised or lowered by a screw (a), by a handle at- 

 tached to it; D, c, E, represent mercurial manometer, a somewhat different form of which is shown 

 in next figure. 



Fio. 133. Diagram of mercurial manometer, a. Floating rod and pen. b. Tube, which com- 

 municates with a bottle containing an alkaline solution, c. Elastic tube and canula; d, the latter 

 being intended for insertion in an artery. 



communicated by means of a lever, , to a writing-needle and registering 

 apparatus. 



FIG. 134. Normal tracing of arterial pressure in the rabbit obtained with the mercurial kymo- 

 graph. The smaller undulations correspond with the heart beats; the larger curves with the 

 respiratory movements. (Burdon-Sanderson.) 



Fig. 136 exhibits an ordinary arterial pulse-tracing, as obtained by 

 the spring kymograph. 



From observations which have been made by means of the mercurial 

 10 



