DIGESTION, CIRCULATION, AND ABSORPTION 285 



Capillaries 



beat per minute when quiet ? What when lightly exercising ? 

 What when more vigorously exercising ? 



Conclusion. Write out your conclusions as to the effect of 

 exercise on the heart action 

 and thus of the pulse. 



Observation. Press a 

 vein in your wrist with one 

 ringer. On side of ringer 

 toward the heart empty the 

 vein by just rubbing an- 

 other finger along it. Does 

 the blood flow back into the 

 vein ? Rub the blood away 

 from the heart, on other side 

 of finger pressing the vein. 

 Does the blood flow back ? 



Conclusion. What is 

 your conclusion concerning 

 the structure and direction 



Lungs 



of blood flow in the veins ? 



c. Study of Chart, and 

 Sheep or Beef Heart 



Method. 1. Refer to 

 any good chart of the cir- 

 culation or to Figure 67 and 

 find the heart, arteries, and 

 veins. Also examine a 

 sheep or beef heart or good 

 model and note the four 

 chambers, the valves, and the blood tubes connected to it. 



Observations. 1. In what direction do arteries lead? 

 Veins ? 



2. Can you make out the heart to be a double force pump ? 

 Study Figure 66. 



FIG. 67. Plan of circulation of blood. 



