226 LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



stomach to the left and the liver to the right. It passes forward imbedded in 

 the liver substance and should be followed by picking away the liver tissue. It 

 receives several hepatic veins from the liver; one of the larger of these lies along 

 the midventral line of the liver and joins the postcaval near the anterior end of 

 the liver. At the anterior end of the liver the postcaval vein emerges as a very 

 large vessel situated in the coronary ligament. It pierces the transverse septum 

 and forks into the two hepatic sinuses which, after being joined by the common 

 cardinal veins, enter the sinus venosus. The origin of the postcaval vein is 

 discussed below. 



c) The posterior cardinal veins: At the place where the postcaval vein turns 

 ventrally toward the liver it is connected with a pair of veins, the posterior 

 cardinal veins. Trace these anteriorly. They he very near the mid-dorsal line 

 of the anterior half of the pleuroperitoneal cavity, one to either side of the dorsal 

 aorta. In females they are situated in the mesotubarium, along the line where 

 this unites with the dorsal wall. Trace the posterior cardinals posteriorly and 

 note connections between them and the renal portal veins (which are of course 

 the original posterior ends of the posterior cardinals, as shown in Fig. 57). Note 

 also the parietal veins which enter the posterior cardinals in their course along 

 the body wall. The posterior cardinals may be traced to the transverse septum. 

 Shortly before reaching this they diverge from each other and penetrating the 

 lateral portions of the septum enter the common cardinal vein practically at the 

 same point as the entrance of the jugular and the subclavian. 



5. The pulmonary veins. — The pulmonary vein is a large vessel situated 

 along the ventral side of each lung, i.e., the side opposite that which is attached 

 to the dorsal wall. The two pulmonary veins run forward in the walls of the 

 lungs and shortly caudad of the transverse septum converge and at the septum 

 unite to one vessel. This passes through the transverse septum and running 

 forward in the dorsal wall of the left hepatic sinus enters the left auricle. 



6. The ventral aorta and the aortic arches. — The conus arteriosus passes 

 anteriorly into the ventral aorta. The greater part of the ventral aorta lies 

 within the pericardial cavity and owing to the fact that this portion of the aorta 

 is expanded and possesses thickened muscular walls, it is named the bulbus 

 arteriosus. 1 Trace the ventral aorta forward out of the pericardial chamber 

 by dissecting away the anterior wall of the chamber. The ventral aorta very 

 soon forks into two vessels which pass to the right and left. Trace the right one, 

 since the visceral arches have been left intact on that side. Follow it toward 

 the gill arches. It soon divides into two vessels and subsequently the posterior 



1 The term bulbus arteriosus is very ambiguously used in many texts of vertebrate anatomy and 

 embryology. The term should be applied only to the expanded muscular base of the ventral aorta. 

 The bulbus arteriosus does not take part in the heart beat and is not a chamber of the heart but a portion 

 of the ventral aorta. This definition does not correspond with the one given in K. Very few groups 

 of vertebrates have a bulbus arteriosus; the chief group possessing it is the Teleostei. The term truncus 

 arteriosus is another ambiguous name. It should probably be used as synonymous with ventral aorta. 



