36 THE SKATE 



to be given off to the viscera. Its chief branches are : the 

 hepatic artery to the liver ; and the anterior gastric divisi- 

 ble into a dorsal gastric and a ventral gastric of the 

 stomach; the splenic; a gastroduodenal with a posterior 

 branch to the posterior part of the stomach, the posterior 

 gastric, pancreatic branch; and a duodenal to that part 

 of the digestive tract. 



The superior mesenteric artery has its origin just pos- 

 terior to the origin of the coeliac and sends branches to the 

 pancreas, and spleen, while its main branch continues to 

 the intestine and the spiral valve. 



The inferior mesenteric artery arises from the dorsal 

 aorta posterior to the superior mesenteric and passes to 

 the rectal gland giving rise to a genital artery which passes 

 to the gonads and their ducts. 



b. Lateral Visceral Branches. Renal arteries are lo- 

 cated on the dorsal side of the kidney. Loosen the kidneys 

 from the body wall and expose these arteries. The genital 

 arteries already located belong to this category. 



c. The Somatic Branches. Several paired parietal ar- 

 teries branch from the dorsal aorta and pass to the body 

 wall, enlarged examples of which are the subclavian to 

 the pectoral fin and the paired iliac arteries to the pelvic 

 fins. The latter arise from the dorsal aorta just anterior 

 to the cloaca and follow a course along the body wall, giv- 

 ing off many branches, some of which unite with the pos- 

 terior end of the ventral abdominal artery before entering 

 the pelvic fin. 



The dorsal aorta continues posteriorly into the tail, 

 v/here it is known as the caudal artery. The injection of 

 yellow paste was made through this artery. 



Drawing 19. Draw the dorsal aorta and its chief branches. 



