440 DISSECTION OF THE PIGEON. 



skull. In its course down the neck it receives 

 veins from the side of the neck and from the 

 crop ; and at the posterior end of the neck it 

 is joined by the vertebral vein, 

 ii. The right brachial vein returns blood from the 



wing, 

 iii. The right pectoral vein is the largest of the 

 three. It returns blood from the pectoral 

 muscles, and receives also the internal mam- 

 mary vein, which runs along the inner surface 

 of the thoracic wall. 



b. The left anterior vena cava returns blood from the 



left side, by veins corresponding to those open- 

 ing into the right vena cava. At the base of the 

 heart, it runs transversely across the dorsal sur- 

 face of the left auricle, to open into the left 

 border of the right auricle. 



To see the opening of the left vena cava into the auricle, 

 lift up the apex of the heart, and turn it forwards. 



c. The posterior vena cava returns blood from the 



posterior part of the body, including the liver. 



It is formed by the union of the two iliac 

 veins a short distance behind the liver. The vein , 

 so formed, runs forwards through the substance 

 of the right lobe of the liver, close to its dorsal 

 surface ; it receives the hepatic veins as it leaves 

 the liver, and then runs forwards as a short wide 

 vessel to open into the posterior surface of the 

 right auricle. 



Tiorn the heart forwards, to expose the posterior vena cava 

 as it enters the right auricle. Follow it back through the 

 liver, slitting it up and washing out the contained blood. 

 Npte the openings of the hepatic veins, and follow them with 

 a seeker into the liver. Follow the vena cava back, behind 

 the liver, to the point where it is formed by the union of the 

 right and left iliac veins. 



