NECTURUS 77 



The latter veins are the postcaval, the posterior cardinal, and 

 the lateral veins. The postcaval is the largest vein in the body ; 

 it begins its course between the kidneys, from which it receives 

 numerous small branches, and runs forward, just ventral to the 

 dorsal aorta, to the middle of the dorsal surface of the liver. Here 

 it turns slightly to the right, enters the liver, and runs through 

 it to its forward end, receiving several hepatic veins. On leaving 

 the liver it becomes much wider and divides into two short trunks, 

 which at once enter the sinus venosus. Find this vein just back of 

 the liver and trace it both ways. 



Between the kidneys and the liver the postcaval receives a 

 number of small genital veins from the reproductive organs and 

 a branch from each of the posterior cardinal veins. 



The posterior cardinals are a pair of veins which arise near the 

 middle of the body and run forward at the right and the left of 

 the median plane and near the dorsal body wall, from the muscle 

 segments of which they receive at regular intervals the parietal 

 veins ; in the female each posterior cardinal lies in the mesentery 

 which joins the oviduct with the dorsal body wall on each side. 

 A short distance in front of the anterior end of the liver each of 

 these veins joins a short transverse vein called the duct of Cuvier, 

 which meets the widened end of the postcaval near its entrance 

 into the sinus venosus. 



The lateral veins are a pair of small vessels, each of which lies 

 beneath the skin along the lateral line; they enter the duct of 

 Cuvier. 



Blood is brought from the forward part of the body by the 

 anterior cardinal and the subclavian veins. The former are a pair 

 of short veins which arise, on eaqh side, by the union of the in- 

 ternal and external jugular veins. The external jugular is the 

 large vein which brings blood from the ventral wall of the mouth ; 

 the internal jugular is a much smaller vein which brings blood from 

 the roof of the mouth and the brain. The subclavian brings blood 

 from the arm on each side ; it and the anterior cardinal meet in the 

 duct of Cuvier. 



The pulmonary vein brings blood to the left auricle from the 

 lungs. It is formed by the union of the right and left pulmonary 



