22 VERTEBRATE ZOOLOGY 



Cut across the main lobes of the liver and near the center 

 of each find the large hepatic sinus. Follow each sinus forward, 

 slitting it open ; at its forward end find, by means of the probe, 

 its opening into the sinus venosus. Note the small veins which 

 are tributary to the hepatic sinus. 



Find the posterior cardinal sinuses ; then the lateral veins and 

 the subclavian veins. The posterior cardinals extend along the 

 entire length of the dorsal wall of the abdominal cavity. Their 

 anterior ends communicate with each other; they are a pair of 

 very wide sacs just behind the false diaphragm and against the 

 dorsal body wall. Posteriorly the sinuses are narrow, being long, 

 slender vessels close to the median line and separated from each 

 other only by the median vertical mesentery. Note the numerous 

 small renal veins which enter them from the kidneys. 



Slit open the right duct of Cuvier, and wash it out if necessary; 

 cut open the saclike anterior end of the posterior cardinal and 

 trace it backward. 



Study the anterior cardinal sinuses, which pass forward either 

 from the ends of the duct of Cuvier or from the posterior cardi- 

 nals. In order to find the anterior cardinal on the right side, turn 

 the animal over so that its dorsal side is uppermost, and make a 

 short, deep, longitudinal incision about halfway between the mid- 

 dorsal line and the foremost gill slits. The anterior cardinal sinus 

 lies just above the gill arches and will be reached by the incision. 

 Probe the sinus back to the duct of Cuvier and slit it open. Follow 

 it forward to the eye, where it opens into the orbital sinus, which 

 surrounds the eyeball. 



Exercise 23. Draw a diagram of the systemic veins, so far as observed. 



The Arterial System. The principal vessels which constitute 

 this system are the following: (i) the ventral aorta, or aorta 

 ascendens, which passes forward from the conus arteriosus; 

 (2) the afferent branchial arteries, which branch off from this 

 aorta and carry venous blood to the gills; (3) the efferent bran- 

 chial arteries, which collect the arterial blood from the gills 

 and carry it dorsally to the mid-dorsal line of the body, where 

 they form (4) the dorsal aorta, or aorta descendens, a median 



