48 PHYSIOLOGY FOR THE LABORATORY. 



3. Imitate in a similar manner any backward pressure 

 in the blood. 



a. What is the effect of the water or blood on the 

 valves ? 



b. What is the action of the valves ? 



c. What is the effect of the valves on the stream of 

 water or blood? 



d. Is your model perfect? If not, what condition of 

 the valves does it illustrate ? 



