COMPARATIVE ANATOMY OF THE CIRCULATORY SYSTEM 211 



side of the kidneys. The kidneys are rounded lobes at the posterior end of the 

 pleuroperitoneal cavity against the dorsal wall. To see them, remove the 

 pleuroperitoneum from the dorsal wall on each side of the cloaca. Do not 

 injure the ducts from the kidneys. After exposure of the kidneys the posterior 

 cardinal veins will be found on the medial side of the kidneys. They connect 

 with each other between the kidneys. 



Return to the common cardinal vein and probe into it in a dorsal direction. 

 Turn the animal dorsal side up and locate the end of your probe. Make an 

 incision into the spot indicated by the probe and extend the incision longitudinally 

 forward to the eye. On carefully deepening the incision an elongated cavity with 

 smooth walls, the anterior cardinal sinus, is exposed. It is situated just medial 

 to the dorsal ends of the gill arches and visceral pouches. It may be followed 

 forward with the aid of the probe. It turns laterally in front of the first visceral 

 pouch, follows along the anterior border of this pouch, and then turns anteriorly 

 again. 



With the dorsal side of the animal still facing you, locate by feeling the 

 chief anterior cartilage (propterygium) of the pectoral fin. It forms a crescentic 

 ridge lateral to the gill region nearly halfway from the mid-dorsal line to the 

 margin. Make an incision along the medial face of this cartilage on the left 

 side. A vein will be exposed running along the cartilage here. It is one of the 

 brachial veins. Follow it posteriorly. It will be found to enter the common 

 cardinal vein. 



Turn the animal ventral side up again. Along the lateral wall of the pleuro- 

 peritoneal cavity runs the lateral abdominal vein. Note the parietal branches 

 which it receives from the body wall at each myoseptum. Trace the lateral 

 abdominal vein anteriorly. It passes along the internal surface of the cartilages 

 of the pectoral fin and pectoral girdle, and enters the common cardinal vein. 

 Cut into the vein where it passes the cartilages. Immediately on the posterior 

 side of the cartilage of the pectoral girdle a brachial vein will be found entering 

 the lateral vein. Immediately posterior to this is another cartilage, and on the 

 caudal side of that another brachial vein joins the lateral vein. A third brachial 

 vein was mentioned in the preceding paragraph. Trace the lateral vein poste- 

 riorly. It originates in a network of small vessels on the sides of the large intestine 

 and cloaca. It passes on the inner surface of the cartilages of the pelvic girdle 

 and pelvic fin. Slit the vein open along the surface of the cartilages. Iliac veins 

 will be found emerging from between the cartilages and entering the lateral vein. 

 The largest of the iliac veins is located along the posterior side of the cartilage 

 of the pelvic girdle. Probe into the iliac veins and note their distribution in the 

 pelvic fin. 



Draw the systemic veins. 



3. The hepatic portal system.— A portal system is a system of veins which 

 flows into a network of capillaries in some organ. The hepatic portal system 



