COMPARATIVE ANATOMY OF THE CIRCULATORY SYSTEM 245 



face of the vertebral column. On separating these muscles in the midventral 

 line, the two arteries may be followed forward. They pass anteriorly side by 

 side. Shortly before they reach the head, they diverge, and at the angle of the 

 jaws each divides into an external carotid, from which branches may be traced 

 to the esophagus, palate, and head generally, and into a more deeply situated 

 internal carotid which passes through the skull to the brain. 

 Draw the branches of the brachiocephalic artery. 



b) The pulmonary arteries: The pulmonary artery passes to the left side of 

 aorta and immediately forks into right and left pulmonary arteries. The left 

 artery goes directly to the left lung. The right artery turns and passing on the 

 dorsal side of the brachiocephalic arteries and posterior to the turn of the aorta 

 enters the right lung. It will be better seen in the next paragraph. 



c) The aorta: The aorta turns to the right, forming what is called the arch of 

 the aorta. This may be followed by cutting across the right precaval vein 

 and the right brachiocephalic artery. The arch of the aorta curves to the dorsal 

 side of the right pulmonary artery, which can now be traced into the lung, 

 and turns caudad. Follow it by dissecting away the tissue between the heart 

 and the right lung and by breaking through the oblique septum. Turn the 

 viscera to the left. Cut through the postcaval vein. The aorta, now called 

 the dorsal aorta, lies in the median dorsal line between the two lungs. It gives 

 off small branches to the esophagus and body wall in its passage along the pleural 

 cavities. At the entrance to the peritoneal cavity the large coeliac artery arises 

 from the aorta. This runs posteriorly along the proventriculus to which it 

 branches. The coeliac artery then gives rise to the relatively small left gastric 

 artery, which passes to the left side of the gizzard branching to this side and the 

 edge of the gizzard. The coeliac artery then passes by the spleen to which it 

 gives small splenic arteries and just beyond the spleen gives rise to the hepatoduo- 

 denal branch. This sends a hepatic branch into the liver and then as the anterior 

 pancreaticoduodenal artery runs along the duodenal loop supplying duodenum 

 and pancreas. The coeliac artery continues as the right gastric, which spreads 

 out over the right surface of the gizzard. The right gastricsends a large posterior 

 pancreaticoduodenal branch to the duodenal loop and pancreas and a mesenteric 

 branch to a loop of the small intestine. 



Very shortly posterior to the origin of the coeliac artery, the superior mes- 

 enteric artery arises from the dorsal aorta and branches to the small intestine. 

 One of these branches passes along the large intestine and anastomoses with the 

 inferior mesenteric artery described below. 



The dorsal aorta now passes between the two kidneys. It gives off on each 

 side the renolumbar artery which supplies the anterior lobe of the kidney and 

 then passes to the body wall and some muscles of the thigh. In female specimens 

 genital arteries are given off to the ovary and oviduct from the renolumbar artery 

 and the renofemoral artery. The renofemoral artery is the large vessel arising 



