62 THE VITAL PROCESSES 



tion. Observe the openings into the auricle, there being one each for 

 the vena cava superior, the vena cava inferior, and the coronary vein. 

 Compare the walls, lining, shape, size, etc., with the ventricle below. 



7. Cut off the end of the left ventricle about an inch above the apex. 

 This will show the extension of the cavity to the apex ; it will also 

 show the thickness of the walls and the shape of the cavity. Split up 

 the ventricular wall far enough to examine the mitral valve and the 

 chordae tendineae from the lower side. 



8. Make an incision in the left auricle. Examine its inner surface 

 and find the places of entrance of the pulmonary veins. Examine the 

 mitral valve from above. Compare the two sides of the heart, part 

 for part. 



9. Separate the aorta from the other blood vessels and cut it entirely 

 free from the heart, care being taken to leave enough of the heart at- 

 tached to the artery to insure the semilunar valve's being left in good 

 condition. After tying or plugging up the holes in the sides of the 

 artery, pour water into the small end and observe the closing of the 

 semilunar valve. Repeat the experiment until the action of the valve is 

 understood. Sketch the artery, showing the valve in a closed condition. 



To illustrate the Action of a Ventricle. Procure a syringe bulb with 

 an opening at each end. Connect a rubber tube with each opening, 

 letting the tubes reach into two tumblers containing water. By alter- 

 nately compressing and releasing the bulb, water is pumped from one 

 vessel into the other. The bulb may be taken to represent one of the 



ventricles. What action of the 

 ventricle is represented by com- 

 pressing the bulb ? By releasing 

 the pressure ? Show by a sectional 

 drawing the arrangement of the 

 valves in the syringe bulb. 



To show the Advantage of the 

 FIG. 25. - Illustrating elasticity of Elasticit y of Arteries. Connect 

 arteries. tne syringe bulb used in the last 



experiment with a rubber tube 



three or four feet in length and having rather thin walls. In the oppo- 

 site end of the rubber tube insert a short glass tube which has been 

 drawn (by heating) to a fine point (Fig. 25). Pump water into the 

 rubber tube, observing : 



i. The swelling of the tube (pulse) as the water is forced into it. 

 (This is best observed by placing the fingers on the tube.) 



