140 Practical Zoology. 



12. In another heart, carefully cut around the base of the 

 pulmonary artery, tie its outer end tightly over the end of a 

 glass tube or spool, and show the action of the semilunar valves, 

 by blowing suddenly and forcibly into the tube. To keep the 

 glass tube from slipping out, slip an inch of thick rubber tubing 

 on the end of the glass tube, so that the rubber tube is even with 

 the end of the glass tube. The valves work better when moist 

 and flexible ; therefore keep the preparation standing in a jar of 

 water until it is to be used. Slit open the artery, and study the 

 valves. 



13. Longitudinal and cross sections of a frozen heart are 

 instructive. 



The Distribution of the Arteries and Veins in the Cat or Rabbit 

 (injected). Directions for injecting are given in suggestions 

 "To the Teacher." i. The main artery, the -aorta, is a thick- 

 walled tube, springing forward from the center of the base of 

 the heart. It soon arches over to the left, and runs along the 

 middle of the dorsal wall of the chest cavity. 



2. At the bend, or arch, the aorta gives off two branches 

 (three in man). The first of these soon subdivides, giving off 

 a branch to the right fore limb, the right subclavian artery ; two 

 branches running along the side of the windpipe are the right 

 and left carotid arteries. The second branch of the aorta runs 

 to the left fore limb, and is the left subclavian artery. 



3. During its course through the thorax the aorta is called 

 the thoracic aorta. Trace it to the point where it runs through 

 the diaphragm. It then becomes the abdominal aorta. Turn the 

 stomach and intestine over to the right, and observe the ab- 

 dominal aorta running along the dorsal wall of the abdomen. 

 Just posterior to the diaphragm, a branch is given off which 

 subdivides, and gives branches to the stomach, liver, and spleen. 

 Farther back a large branch is given off to the small intes- 

 tine. Follow it as it branches into the mesentery. This is the 

 anterior mesenteric artery. Find the branches of the aorta that 

 lead to the kidneys, the renal arteries. Some other branches may 



