THE CIRCULATION OF THE BLOOD. 37 



the large chamber of the heart on the right side of the 

 heart, (A in Fig. 3.) 



h. The left ventricle is the corresponding chamber on 

 the left side. Which ventricle has thicker walls ? Why ? 

 Do they both extend to the apex of the heart ? (B in 

 Fig. 3.) 



i. The right and the left auricles are the thin-walled 

 pouches at the base of the heart. They may be partly 

 cut away in your specimen. (C and D in Fig. 3.) 



j. Sketch a dorsal and a ventral view of the heart. 



C. The Blood- Vessels that Open into the Heart. 



Materials. The heart and lungs of a calf, neither cut nor punc- 

 tured in any way, but with the pericardium removed. 



Apparatus. A piece of glass tubing drawn out to a point 'for a 

 blowpipe or a metallic blowpipe. 



Identify : 



a. The inferior vena cava is the large vein that comes up 

 from the lower part of the body and carries the impure 

 blood into the right auricle. Look for it on the dorsal 

 side of the right auricle at its extreme left where it joins 

 the right ventricle. With a blowpipe inflate the auricle 

 through the inferior vena cava. (E in Fig. 3.) 



6. The superior vena cava carries the blood from the upper 

 part of the body into the right auricle. Look for it close 

 beside a, but at the part of the right auricle that is farthest 

 from the apex of the heart. Follow it away from the 

 heart, as far as you can, to its source at the union of 

 the two innominate veins. With the blowpipe inflate the 

 auricle through this vein. (F in Fig. 3.) 



