444 DISSECTION OF THE PIGEON. 



along the side of the neck, in the vertebrar- 

 terial canal of the cervical vertebraB. 



Opposite the angle of the jaw, the carotid 

 artery divides into external and internal 

 carotid arteries, 

 a. The external carotid artery supplies the 

 tongue, the muscles of the jaws, and other 

 parts of the head. 

 y8. The internar[oarotid artery enters the skull 

 by a foramen in its base, and supplies the 

 brain. 

 . ii. The subclavian artery, which is much the larger 

 of the two branches of the innominate, runs 

 outwards, and divides, after a course of not 

 more than an eighth of an inch, into the 

 brachial and pectoral arteries, 

 u,. The brachial artery runs straight outwards to 

 the wing, giving a branch to the shoulder- 

 joint. 

 p. The pectoral artery is a large vessel, very 

 little smaller^ than the innominate itself: 

 it runs outwards and backwards, looping 

 round the outer side of the sternal end of 

 the coracoid, to enter the deeper surface 

 of the great pectoral muscle, in which it 

 divides into numerous branches. 



b. The right innominate artery has branches exactly 



corresponding to those of the left innominate. 



c. The dorsal aorta, which is rather smaller than 



either of the innominate arteries, arches over to 



the right side, crosses the right pulmonary artery, 



and then runs backwards along the mid-dorsal 



line of the thorax and abdomen. Its principal 



branches are as follows. 



i. The coeliac artery is a median vessel which arises 



about the level of the auriculo-ventricular 



septum of the heart. It runs back in the 



