THE DOGFISH 21 



aorta, which lies just above it, are inclosed in the cartilaginous 

 arches of the ventral side of the vertebrae. The caudal vein enters 

 the abdominal cavity at its hinder end and at once divides into a 

 right and a left renal vein, each of which passes to the dorsolateral 

 side of a kidney and sends numerous branches into it along its 

 entire length. 



Exercise 22. Draw a diagram of the renal portal system. 



The Systemic Veins. These veins, which form the main venous 

 system, are characterized by their great size, being in some places 

 so wide that they are called sinuses. The latter include a pair of 

 anterior and a pair of posterior cardinal sinuses, which bring blood 

 from the anterior and posterior parts of the body respectively. The 

 anterior and posterior cardinals on each side meet in a common 

 transverse sinus called the duct of Cuvier, which extends from the 

 end of the sinus venosus dorsally and laterally. Opening into 

 the sinus venosus, also, near the median plane is a pair of 

 hepatic sinuses, which bring blood from the liver. The cardinal 

 vessels are dorsal in position, and the hepatic sinuses are ventral. 



Entering the anterior end of the posterior cardinal sinus from 

 behind, on each side, are the lateral vein and the subclavian vein. 

 The former will be seen extending along the inner surface of 

 the wall of the abdominal cavity from one end of it to the other, 

 opposite the lateral line ; the latter lies along the pectoral girdle 

 and brings blood from the pectoral fin. The iliac vein, which 

 brings blood from the ventral fin, enters the lateral vein. Find 

 these veins. 1 



Cut away enough of the pectoral girdle and ventral body wall 

 to give free access to the interior of the pericardial cavity ; note 

 the sinus venosus as it stretches across the hinder end of the cavity, 

 to the dorsal wall of which it is^ attached. Slit open the sinus 

 venosus, exposing its inner surface, and wash it out if necessary. 

 Note its extension at each side in a dorsal direction to form the 

 duct of Cuvier ; probe this duct. 



1 These veins and sinuses can usually be studied without injection, because 

 they are colored by the blood in them. If it is desired to inject them, this may be 

 done through the lateral vein. 



