56o MAMMALS. 



The aortic trunk 



gives off the innominate artery, 



which divides into (a) the right subclavian, continued as the 

 brachial to the fore-limb, but giving 

 off the vertebral to the spinal cord 

 and brain, and the internal mam- 

 mary to the ventral wall of the 

 thorax : 

 (b) the right carotid, running along the 

 trachea, dividing into the right 

 internal carotid to the brain, and 

 the right external carotid to the 

 head and face : 

 (<■) the left carotid, with a similar course: 

 thereafter the aorta gives off 



the left subclavian artery, with branches like the right, 

 the cceliac artery to the liver, stomach, and spleen, 

 the anterior mesenteric to the pancreas and intestine, 

 the renal arteries to the kidneys, 



the spermatic or ovarian arteries to the reproductive organs, 

 the posterior mesenteric to the rectum, 

 the lumbar arteries to the posterior body-walls. 

 The aorta is continued terminally in the median sacral artery to the 

 tail, and laterally in the common iliacs which form the femorals of 

 the hind-legs, and give off in the abdomen several branches to the ab- 

 dominal walls, the pelvic cavity, the bladder, and the uterus. 



The Venous System. The two superior vense cavie bring blood from 

 the head, neck, thorax, and fore-limbs. Each is formed from the 

 union of 



a subclavian from the shoulder and fore-limb, 



an external jugular from the face and ear, 



an internal jugular from the brain, 



an anterior intercostal from the spaces between the anterior 



ribs, 

 an internal mammary from the ventral wall of the thorax ; 

 and the right superior vena cava also receives an azygous cardinal vein, 

 which runs along the mid-dorsal line and collects blood from the 

 posterior intercostal spaces. 



The inferior vena cava is a large median vein lying beside the aorta 

 beneath the backbone. Anteriorly it is embedded in the liver, and re- 

 ceives the hepatic veins. Thence it passes through the diaphragm into 

 the right auricle. Posteriorly the inferior vena cava has the following 

 components : — 



internal iliacs from the back of the thighs, forming by their union 



the beginning of the inferior vena cava ; 

 femoral veins from the inner borders of the thighs, continued into 



external iliacs which open into the inferior vena cava ; 

 paired ilio-lumbars iirom the posterior abdominal walls ; 

 spermatic or ovarian veins from the reproductive organs ; 

 renal veins from the kidneys. 

 There is no renal portal system. 



