PROBLEM 3. How Materials Are Moved to a?id from Cells 225 



6. To see the heart beat in the frog. Dissect a frog as directed on page 

 202. Though the frog is completely dead, its heart continues to beat for 

 hours, especially if kept in Ringer's or Locke's solution. The frog's heart 

 is more nearly triangular than ours. It has two auricles but only one ven- 

 tricle. In which part does the beat start? Do the two auricles contract 

 separately or together? Which contracts more forcibly, auricles or ven- 

 tricle? How long is the pause between heart beats? How could you ex- 

 plain this? What difference is there in the color of the auricles and the 

 ventricle? Explain. 



7. What is the effect of various activities upon the pulse rate? To take 

 your pulse place the tips of your fingers (except the thumb) on the inner 

 part of your left wrist below the base of the thumb. Why can the pulse 

 be felt easily here? Where else may the pulse be taken? Take your pulse 

 while lying do\\n, \\'hile sitting quietly, while standing quietly for five 

 minutes, after bending and touching the floor five times, after running 

 swiftly for a short distance, after listening to some exciting event over 

 the radio, and so on. Vary the activity in any way that is convenient. 

 Record your observations. Explain the differences. Compare your sitting 

 pulse rate with that of the other students. What is the most common rate 

 for your group? 



8. How can you demonstrate the presence of valves in the veins? Find 

 a place on your arm or hand where the veins show most prominently. 

 Place your thumb on one vein and while pressing down slide it toward 

 the fingers. Observe what happens. Release the pressure. What happens 

 now? Repeat this several times using different veins. What conclusions 

 can you draw from your observations? 



9. Copy Figure 220 which shows the course of blood from the left 

 ventricle to right auricle. Now draw in Figure 221 fitting it together with 

 the first. Color with red crayon all blood which carries much oxygen. 

 Color with blue all vessels carrying blood which has lost its oxygen. 

 Under your diagram list the arteries which carry bright red blood. Now 

 list arteries and veins which carry blood that has lost its bright red color. 



Further Activities in Biology 



1, Could you make a chart showing the blood vessels as roads, a few 

 scattered cells to which goods are delivered as buildings, and the transpor- 

 tation of goods to and from the cells? 



2, Report on the life and work of William Harvey. 



3, Report on some of the theories of the circulation of blood before 

 Harvey's time. (See Locy, Biology and Its Makers.) 



4, Look up and report on blood transfusions. 



5, Make a model of a human heart. 



