THE CIRCULATION OF THE BLOOD 



87 



The bulb may be pumped weak or strong, fast or slow, while the 

 peripheral resistance may be high or low. We have, therefore, a 

 contrivance through which we are able to vary one factor at a time. 



The arterial manometer should have limbs not less than 50 cm. 

 in length, while those of the venous manometer need not be more 

 than one-half that length. These manometers may be held by 

 clamps to chemical stands which are on or beside the table. 



2. Preparation. Set up an artificial circulatory system as shown 

 in Fig. 48. 



FIG. 48 



FIG. 49 



Artificial circulatory system, described in detail in text. 



Mercury manometer. 



After the system is set up make a study of the mercury manom- 

 eters, the instruments with which the pressure is to be measured. 



The specific gravity of mercury is approximately 13.6. What is 

 the gas pressure at n that will cause a rise of 4 cm. of mercury in 

 the distal tube? (See Fig. 49.) 



What is the water pressure at n that will cause a rise of 6 cm. of 

 mercury in the distal tube? 



What is the water pressure at n that will cause a rise of m cm. of 

 mercury in the distal tube? 



After the system has been freed from air and is at rest, do the 

 proximal and distal columns of mercury in the arterial manometer 



