REPTILIA 



569 



carotids pass laterally and parallel with the corresponding aortic 

 arches. At the distal end of the common carotids each anastomoses 

 with the corresponding aortic arch. 



The right and left subclavian arteries arise from the right aortic 

 arch just anterior to its junction with the left aortic arch to form the 

 dorsal aorta. Each passes laterally ; one to each of the forelimbs. 



The dorsal aorta is a median, unpaired, longitudinal artery lying 

 in the mid-dorsal line ventral to the vertebral column. A little 

 further caudal small gastric arteries pass to the stomach. Near the 

 posterior end of the stomach the large coeliac artery is given off. This 

 soon divides into two trunks. The anterior coeliac artery supplies 

 the digestive glands, stomach, and duodenum. The posterior branch, 

 the ventral gastric supplies the ventral surface of the stomach. The 

 anterior mesenteric is the next unpaired branch of the aorta and it 

 soon divides into the hepatoduodenal to the left side of the liver and 

 the duodenum, and the superior mesenteric to the ileum. The right 

 hepatic artery springs from the dorsal aorta and passes to the right 

 lobe of the liver. The inferior mesenteric arteries include three small 

 vessels arising from the dorsal aorta at the level of the pelvis, which 

 supply the large intestine and rectum. Two pairs of small branches, 

 the genital and renal arteries, supply the gonads and kidneys re- 

 spectively. The right and left iliac arteries branch from the aorta 

 and pass into the respective hindlimbs and bifurcate to become fem- 

 oral and sciatic artery of each limb. Further posteriorly the dorsal 

 aorta continues into the tail as the caudal artery. 



The veins of the body, with the exception of the pulmonary veins, 

 enter the sinus venosus. This is a thin-walled chamber located dor- 

 sally to the right auricle. It communicates with the right auricle by 

 means of the sinuauricular aperture. This aperture is guarded by 

 the two-lipped sinuauricular valve. 



The pulmonary veins bring blood from the lungs. They unite into 

 a short common trunk which enters the left auricle on its dorsal wall. 



The postcaval vein, which receives the wide hepatic vein from the 

 liver, extends from the anterior border of the liver to the sinus 

 venosus. Posteriorly it lies between the gonads, and is formed by 

 the union of a pair of efferent renal veins which lie parallel to the 

 epididymis or oviducts. The postcava also receives a spermatic or 

 ovarian tributary from each gonad. 



