210 LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



lateral margin of the cloacal aperture, and near the anterior part of the base of 

 the pelvic fin receives the iliac vein from the fin. Trace this according to the 

 directions for the spiny species. 



In the median ventral line are traces of a ventral cutaneous vein which seems, 

 however, to dwindle away anteriorly. 



Draw the systemic veins. 



Skate: The sinus venosus consists of a tube on each side, the central portion 

 being reduced in size and attached to the transverse septum by a sheet of connec- 

 tive tissue which may be broken. Each side of the sinus is buried in the trans- 

 verse septum. Follow out the right side to the point where it disappears dorsal 

 to the cartilage of the pectoral girdle. Carefully shave away the cartilage and 

 surrounding tissues until the sinus venosus can be followed laterally. Insert one 

 blade of a fine scissors in the ventral wall of the sinus and slit it open in a cross- 

 wise direction. The sinus is seen to be continuous on each side with a tube or 

 chamber, the common cardinal vein or duct of Cuvier, which turns dorsally. All 

 of the systemic veins open into the common cardinal vein, and their openings 

 may now be identified. The junction of common cardinal vein with the sinus 

 venosus is marked by a slight fold. In the anterior wall of the common cardinal 

 vein concealed by this fold is the small opening of the inferior jugular vein. This 

 opening is so small that the probe can probably not be passed into it. The 

 inferior jugular vein drains the walls of the pericardial cavity and the floor of 

 the mouth and pharyngeal cavities. In the posterior wall of the common cardinal 

 vein, at its junction with the sinus venosus, is the opening of the hepatic sinus. 

 Probe posteriorly into this. It leads into the hepatic sinus, a large space situated 

 between the anterior margin of the liver and the transverse septum and inclosed 

 by the coronary ligament. In females the hepatic sinus lies dorsal to the mouth 

 of the oviduct which is inclosed in the falciform ligament. In locating the hepatic 

 sinus press the liver caudad away from the transverse septum ; the sinus forms a 

 bag between liver and septum ventral to the esophagus. Cut into the hepatic 

 sinus. A tube, the pericardio-peritoneal canal, extends through the center of its 

 cavity. Look in the posterior wall of the sinus for the small openings of the 

 hepatic veins which drain the liver. The sinus opens on each side into the 

 common cardinal vein. 



Now probe into the main cavity of the common cardinal vein in a dorsal 

 and posterior direction. The probe enters the posterior cardinal sinus which is 

 a broad, thin-walled tube lying against the dorsal wall of the pleuroperitoneal 

 cavity. In females it is on the dorsal side of the oviduct; in males, dorsal to 

 the testis. Follow the posteror cardinal sinus posteriorly. It swerves toward 

 the median line where it soon meets its fellow of the opposite side to form a single 

 large median sinus. This sinus communicates on its ventral surface with the 

 large genital sinus surrounding each gonad. More posteriorly the posterior cardi- 

 nal sinus separates again into two veins which proceed caudad on the medial 



