THE CIRCULATION OF THE BLOOD 



83 



Use a time unit of ten seconds. Repeat each observation at least 

 three times. 



(3) From the above results compare influence of a varying radius 

 when the height is constant i. e., discharge at h = 36, through 

 6-mm. nozzle; through 3-mm. nozzle. 



D : d : : E 2 : r 2 . 



(4) Having tested the two variables separately, test the two com- 

 bined variables. 



D : d : : E 2 y H : r 2 !/h. 



(5) To determine the relation of discharge to resistance: Attach 

 to the larger nozzle one length of 6-mm. tubing. Note the discharge 

 in, say, ten seconds. Attach a second length of 6-mm. tubing, taking 

 care that the tubing is approximately horizontal. Note the dis- 

 charge in the same length of time. What is your conclusion? Why 

 does the discharge decrease when the length is increased? 



FIG. 46 



Reservoir with piezometers. 



(6) To measure the pressure at various points along the course 

 of the discharge tube: (a) Insert a 6-mm. T-tube with an upright 

 limb not less than 50 cm. in length between the two 6-mm. discharge 

 tubes. Is the height of the water in the upright (piezometer) as 

 great as in the reservoir? (b) Add another T-tube to the end of 

 the second 6-mm. discharge tube; how high does the water rise in 

 the second piezometer? Comparing the height of the water in the 

 reservoir and the two piezometers, what are your conclusions as 

 to the pressure in different parts of the discharge tube? 



(7) By leaving out the 50 cm. tubes and setting the T-tubes end 

 to end thus (J. _L _L JL _L _L) a set of piezometers similar to those shown 

 in Fig. 46 can be set up and new observations made. 



