BLOOD PRESSURE. 



75 



rubber tubing nearest the heart takes the place of the arterial 

 system, while the venous system is the tubing on the other side 

 of the resistance. 



1. With moderate capillary resistance determine a rate of bulb 

 compression which will cause a pronounced rise in pressure as 

 shown by the manometer. (If possible both arterial and venous 

 manometers should record in line vertically with each other; to 

 do this the arterial pressure zero should be higher than that for 

 the venous pressure.) By means of the block vary the ampli- 

 tude, but maintain a constant rate. What do the records of 

 venous and arterial pressure show? What can you say in 

 regard to the venous outflow? 



2. With the same capillary resistance and with a moderate 

 amplitude vary the rate. Obtain pressure records and note 

 venous flow. 



3. Wi,th the rate which gives the best results and with moderate 

 amplitude vary the capillary resistance, recording pressure 

 changes and noting venous outflow as before. 



B 



z> 



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FIG. 22A. 





Compare diastolic and pulse pressures under the foregoing 

 conditions. 



What relation does capillary resistance bear to them? 



How do amplitude and rate of the heart contraction affect 

 diastolic and pulse pressures? 



Experiment 33a. The apparatus represented in Fig. 22a may 

 be employed to demonstrate the part which the peripheral 

 resistance and the elasticity of the arterial walls play in the 



