THE CIRCULATION OF THE BLOOD 551 



The upstroke is unusually high and quick. It 

 is at once followed by a great and sudden fall. 

 Obviously a relatively empty artery has been 

 suddenly filled by an unusually large inflow and 

 has been suddenly emptied again through the 

 broken valve and the capillaries. The pulse- 

 curve shows low arterial tension, but is of greater 

 amplitude than the pulse in which low tension 

 results from lowering the peripheral resistance. 

 In the body, the amplitude of the pulse in aortic 

 regurgitation is increased by the greater force 

 with which the ventricle contracts, as well as by 

 the larger quantity discharged at each beat, for 

 the back-flow from the aorta dilates the ventricle 

 and usually causes the walls of the ventricle to 

 increase in thickness (dilatation with hypertrophy 

 of the ventricle). 



Stenosis of the Aortic Valve. Replace the rub- 

 ber flap upon the aortic valve-tube, and tie a 

 string around the flap and tube just over the 

 opening in the tube. Stenosis, i. e. narrowing, of 

 the opening will thus be secured. Put the valve- 

 tube in place, and compress the bulb at the usual 

 raie. Record pulse curves. 



The slow difficult, emptying of the ventricle 

 will be evident in the curve and to the hand. 

 The movements of the arterial manometer are 

 sluggish and of diminished amplitude. The 



