31^ 



CHORD AT A. 



column till it terminates in the caudal. It gives off a media] 

 coeliac to the stomach, a superior mesenteric to the spleer 

 pancreas and intestine, paired renals to the kidneys an< 

 paired iliacs to the pelvic fins. These arteries are full 

 exposed by removal of the coracoid bar and, if necessary 

 the pubic bar. 



We may note some special features of the blood-vascula 

 system of the skate which are also typical of the class. Thi 

 blood-vascular system can be divided into the arterial an( 

 the venous system as in all Vertebrata^ but the venous systen 



Fig 228. — Diagram of the Venous System of a Skate. 



Hepatic Sinus. 



Brachial. 



Renal Portal. 



Pelvic. 



Caudal. 



is chiefly composed of wide sinuses (also a common condi 

 tion of invertebrates). The arterial system has two distinct 

 parts separated by the capillaries of the gills. The ventrai 

 or afferent branchial system carries venous hlood for7vards tc 

 the gills; the dorsal or efferent branchial system carries 

 blood mostly backwards to the system. In the venous 

 system the capillaries of the liver and those of the kidney 

 both break up the continuity of the sinuses, forming a 

 hepatic-portal and renal-portal system respectively. 



