THE CIRCULATORY SYSTEM 29 



turn the skate over and locate the end of the probe. Make 

 a longitudinal incision at the end of the probe and run it 

 forward to the eye. This exposes the anterior cardinal 

 sinus, which is a smooth-walled elongated cavity situated 

 between the dorsal ends of the visceral pouches. 



A branch of the brachial vein may be located on the dor- 

 sal surface. Make an incision along the medial face of the 

 anterior cartilage of the pectoral fin and locate this vein. 

 It runs into the common cardinal vein. 



Within the pleuroperitoneal cavity a few other veins may 

 be located. On the lateral wall is the lateral abdominal 

 vein which receives a parietal branch from each myosep- 

 tum. It originates near the cloaca. It passes along the 

 internal surface of the pectoral fin cartilage and extends 

 to the common cardinal vein. Brachial veins will be found 

 joining the lateral abdominal vein. One may be located 

 on the posterior side of the pectoral girdle cartilage. 

 There are others. The largest of the iliac veins will be 

 found along the posterior side of the cartilage of the 

 pelvic girdle. The iliac veins come from the pelvic fin. 



Deawinq 14. Outline the systemic veins. 



B. The Portal Systems, 



In the skate there are two portal systems, the hepatic 

 portal and the renal portal. The hepatic portal system 

 collects the venous blood from the various parts of the 

 digestive tract and spleen and carries it into the liver, 

 where it breaks up into a network of capillaries which are 

 collected later and enter the hepatic sinus. 



a. The Renal Portal System. Study the renal portal 

 system from the figure. It consists of a caudal vein which 

 collects the blood from the caudal region and runs forward 

 to the cloacal aperture, where it forks into the two renal 

 portal veins extending to the ventral side of the kidney 



