THE PIGEON. 239 



245. The left precaval vein (vena cava superior s. 

 anterior sinistra), (l.prc\ similarly related to the left innomi- 

 nate artery, and receiving veins symmetrical with those of 

 its fellow : it passes backwards to the dorsal side of the 

 heart, \\here its further course will be seen subsequently 



( 254). 



246. The postcaval vein (ptc) has already been seen 

 ( 215) : after emerging from the liver it passes directly 

 forwards and enters the right auricle on the right side of 

 its dorsal wall. 



247. The course of the common carotid arteries 

 (c.c), made out by removing the crop and dissecting away 

 the ventral muscles of the neck : each passes forwards and 

 inwards towards the middle line of the neck, and runs 

 parallel and close to its fellow along the ventral aspect of 

 the cervical vertebrae : about an inch behind the head, the 

 arteries diverge again, and each, passing forwards and 

 slightly outwards, divides into an external carotid (e.c), 

 supplying the head generally, and an internal carotid 

 (i.t), supplying the brain. 



248. The vertebral artery (vr\ arising from the common 

 carotid in the root of the neck : it passes to the lateral aspect 

 of the neck, and, dipping between the muscles, enters the 

 vertebrarterial canal, and passes forwards to supply the 

 brain and spinal cord. 



249. The course of the jugular veins (ju) : they are 

 united with one another by a transverse commissure (ju') on 

 the under surface of the skull just behind the velum palati 

 ( 299); this is best seen by dissecting away the anterior 

 part of the gullet from the neck muscles and turning it as 

 far forwards as it will go. 



The commissural branch receives veins from the palate, and the 

 jugulars themselves from various -parts of the head : further back each. 



