EESPIRATORY WAVE IN BLOOD-PRESSURE CURVE. 297 



The character of the change in pressure which accompanies the 

 heart's systole is not exactly shown in the tracing obtained by the 

 mercurial manometer, owing to the sluggishness of the movement 

 of the mercurial column, which, as it were, rubs off the apices of 

 the curves. But, with the spring Kymograph of Fick, the de- 

 tails of these oscillations are marked. They are, of course, syn- 



FIG. 136. 



Fick's Spring Manometer. A hollow C-shaped spring (A), made of ex- 

 tremely thin metal, is fixed at (b b) where its cavity communicates with 

 the tube (K). The top of the C is connected at (a) with the writing lever. 

 Any increase of pressure in the tube (K) causes the spring to expand and 

 move the writing point (G) up and down. 



chronous with the arterial pulse, and follow the variations of ten- 

 sion, as will be described when treating of that subject. (See 

 Figs. 136 and 137.) 



The cause of the undulations in the blood-pressure curve cor- 



25 



