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EXPERIMENTAL PHYSIOLOGY 



FIG. 68. Diagram of Fick's C-spring kymograph. Any increase of pressure 

 within the hollow metal spring (which is filled with fluid) causes the C to 

 open ; any decrease of pressure causes it to close. These movements are 

 communicated to the lever. The advantage of employing this or other 

 spring manometers is that they have less inertia than the mercury kymo- 

 graph. They must, however, be graduated by aid of a mercury manometer. 



FIG. 69. Diagram (after Schenck) to show the principle of the Hiirthle kymo- 

 graph, a, Tube terminating above in a tambour4ike enlargement covered 

 by a stout rubber membrane upon which is a metal disc and a wedge 

 actuating a very light lever. The tube is connected by rubber pressure 

 tubing with a cannula like that shown in Fig. 67, and the whole is filled 

 with sodium bicarbonate solution. 



