THE RABBIT 293 



The Anterior Arteries. We have already noted the three (in 

 some rabbits two) large arteries which branch from the arch of 

 the aorta: the innominate artery, at the animal's right, and the 

 left common carotid (which may, however, branch from the in- 

 nominate instead of from the aorta) and left subclavian arteries, 

 at its left. The innominate almost immediately divides (in most 

 rabbits) into two branches: the right subclavian artery, which 

 carries blood to the right foreleg, and the right common carotid 

 artery, which carries it to the head. 



Follow the right subclavian artery and its branches. From its 

 hinder surface near its base the internal mammary and anterior 

 intercostal arteries leave it together, the former passing posteriorly 

 along the ventral thoracic wall into the abdomen, where it anas- 

 tomoses with the epigastric artery ; it will not be seen, because of 

 the removal of the ventral thoracic wall. The anterior intercostal 

 artery proceeds to the dorsal thoracic wall, where it gives off three 

 or four intercostal arteries. From the anterior surface of the sub- 

 clavian at the same place the vertebral artery passes dorsally to 

 the vertebrarterial canal of the cervical vertebrae, through which 

 it goes to the head. After giving off several arteries which pass to 

 the muscles of the neck and thorax, the subclavian artery becomes 

 the axillary, and passing through the brachial nerve plexus it 

 enters the leg, where it becomes the brachial artery ; follow it into 

 the leg and note its branches. 



Follow the right and left common carotid arteries forward as 

 they pass to the head, one on each side of the trachea ; note the 

 branches each sends off. 



Exercise 16. Draw a diagram showing the subclavian and common 

 carotid arteries and their branches, so far as observed. 



The Internal Structure of the Heart. Remove the heart from the 

 body, cutting its veins and arteries a short distance from it, and 

 dissect it under water. Pin the heart with the ventral side upper- 

 most and thoroughly dissect away the loose tissues from the 

 stumps of the aorta and the pulmonary artery. Pin the heart with 

 the dorsal side uppermost ; identify and clean the stumps of the 

 precaval, postcaval, and pulmonary veins. 



