SEC. 4. THE PULSE. 



139. We have seen that the arteries, though always dis- 

 tended, undergo at each systole of the ventricle a temporary 

 additional distension, a temporary additional expansion so that 

 when the finger is placed on an artery, such as the radial, an 

 intermittent pressure on the finger, coming and going with the 



FIG. 42. FICK'S SPRING MANOMETER. 



The flattened tube in the form of a hoop is firmly fixed at one end, while the 

 other free end is attached to a lever. The interior of the tube, filled with spirit, is 

 brought, by means of a tube containing sodium carbonate solution, into connection 

 with an artery, in much the same way as in the case of the mercury manometer. 

 The increase of pressure in the artery being transmitted to the hollow hoop, tends 

 to straighten it, and correspondingly moves the attached lever. 



