CIRCULATION IN BLOOD-VESSELS 



79 



FIG. 65. DIAGRAM OP FICK'S O-SPRING KYMOGRAPH. ANY INCREASE OP PRESSURE WITHIN THE 

 HOLLOW METAL SPRING (WHICH is PILLED WITH FLUID) CAUSES THE TO OPEN ; ANY DECREASE 

 OP PRESSURE CAUSES IT TO CLOSE. THESE MOVEMENTS ARE COMMUNICATED TO THE LEVER. 

 THE ADVANTAGE OP EMPLOYING THIS OR THE HURTHLE MANOMETER IS THAT THEY HAVE LITTLE 

 INERTIA AS COMPARED WITH THE MERCURY KYMOGRAPH. THEY MUST, HOWEVER, BE GRADUATED 

 BY AID OP A MERCURY MANOMETER. 



FIG. 66. DIAGRAM (AFTER SCHENCK) TO SHOW THE PRINCIPLE OP THE HPRTHLE KYMOGRAPH, a, 



TUBE TERMINATING ABOVE IN A TAMBOUR-LIKE ENLARGEMENT COVERED BY A STOUT RUBBER 



MEMBRANE UPON WHICH is A METAL DISK AND A WEDGE ACTUATING A VERY LIGHT LEVER. 

 THE TUBE is CONNECTED BY RUBBER PRESSURE TUBING WITH AN ARTERY CANNULA LIKE THAT 



SHOWN IN FIG. 64, AND THE WHOLE IS PILLED WITH SODIUM BICARBONATE SOLUTION. 



