150 ELEMENTARY PHYSIOLOGY. [XIV. 



On the strokes ceasing, the mercury gradually 

 falls until the previous level is reached. 

 In V the mercury rises to a much less extent 

 than was the case in a, a slight mean pressure 

 much less than in A is established, marked 

 either with no oscillations at all or such as 

 are much less conspicuous than those of A. 

 Owing to tJie presence of the resistance, a mean 

 pressure (arterial blood pressure) is establislied on 

 the proximal (arterial) side of the resistance. 

 This pressure is marked by oscillations syn- 

 chronous with the strokes of the pump. On the 

 distal (venous) side the mean pressure is much 

 less and the oscillations are either slight or 

 altogether absent. 



2. Flow from Arteries and Veins. 



Remove the clamps from the fine nozzles a and v. 

 Let the clamps c, c and c" remain closed. Set 

 the pump going. The flow from a on the 

 proximal (arterial) side is in jets ; that from v 

 (venous) side is uninterrupted or nearly so. 



3. Sphygmograph. 



Bring the levers S a (arterial side) and S v (venous 

 side) to write on the revolving drum, one under 

 the other. 



a. Open the clamps c, c' and c", and set the pump 

 going. The two levers describe two nearly 

 straight lines, a slight rise only being evident 

 (and that to about the same extent in both) 

 at each stroke. 



