BLOOD VESSELS. CIRCULATION 87 



to fill the system, the pump is disconnected and the 

 tubing connected with a water tap. 



When the system has been filled with water, connect 

 the pump, and set the motor in action. 



1. With tap T closed, observe: 



a. The large rise of pressure in the arterial mano- 

 meter (arterial pressure) and the difference between the 

 pressure during the stroke of the pump (systolic pres- 

 sure) and after it (diastolic pressure). The mean of 

 the systolic and diastolic pressure is the mean arterial 

 pressure. The difference between the systolic and the 

 diastolic pressure is the pulse pressure. 



6. The small pressure in the venous manometer and 

 the absence of pulse variation. (For complete absence 

 of venous pulse in the scheme the elasticity of the ar- 

 terial tube must be high.) 



c. The rise of the lever connected with the plethys- 

 mograph and its correspondence with the pulse waves. 



2. Note by the rise of the levers L and L 2 the time 

 taken by the pulse wave to travel through the arterial 

 tubing; this may be recorded on a revolving drum, or 

 taken with a stop-watch. Inject a little coloured fluid 

 into the arterial tube near its origin and note the time 

 of its first appearance in the capillary tubes. Compare 

 the rate of travelling of the fluid with that of the pulse 

 wave. 



3. Increase the rate of thrust of the pump, and ob- 

 serve the rise of mean arterial pressure and the decrease 

 of the pulse pressure. 



4. Open gradually the tap T to increase the resist- 

 ance, and observe the fall of arterial pressure, the rise 



