34S DISSECTION OF THE RABBIT. 



and returns blood from the terminal portion 

 of the rectum. 

 3. The pulmonary system consists of the pulmonary veins, 

 which have already been described (p. 341). 



C. The Arteries. 



The arteries form two distinct systems, of which one, the 

 aortic system, conveys arterial blood from the left ventricle to 

 all parts of the body ; while the other, or pulmonary system, 

 carries venous blood from the right ventricle to the lungs. 

 The arteries are thicker-walled, and hence paler in colour, 

 than the veins. 



The aortic system should be dissected first. Glean the 

 aorta along its whole length, and follow tJie arteries arising 

 from it to their distribution. 



During the dissection of the arteries, take great care not to 

 damage or remove the nerves lying near them. 



1. The aorta arises from the base of the left ventricle, and, 



turning towards the left side to form the arch of the 

 aorta, runs backwards through the thorax and abdo- 

 men. It lies on the ventral surface of the vertebral 

 column, and divides about an inch in front of the 

 level of the pubic symphysis into the two common 

 iliac arteries. 



2. Arteries arising from the aorta in the thorftx. 



a. The innominate artery arises from the commence- 

 ment of the arch of the aorta : it gives off, close 

 to its origin, the left carotid artery, and then runs 

 forwards a short distance and divides into the 

 right subclavian and right carotid arteries, 

 i. The right subclavian artery runs outwards just 

 in front of the first rib : it gives branches to the 

 shoulder, and runs on as the brachial artery 

 into the right fore-limb. Its principal branches 

 are the following. 



