90 



ANATOMY OF VERTEBRATES. 



and integuments of the side of the neck, its branches are dis- 

 tributed, anastomosing with the superior oesophageal and tracheal 

 arteries. Sometimes, in the Duck, the supra-scapular artery, 

 which is usually divided from the vertebral, is a branch of the 

 common trunk, as it is also in the Apteryx, where it supplies the 

 muscles at the back of the base of the neck. 



Birds, as a rule, are peculiar in sleeping with their long neck 



much bent or twisted, and 

 this position might be ex- 

 pected to exercise some 

 effect on the vessels sub- 

 ject thereto. Accordingly 

 we find that the carotid 

 arteries, ib. 4, fig. 90, u, u, 

 are frequently of unequal 

 size ; in the Dabchick the 

 left is the largest, fig. 93, 2 ; 

 in an Emeu I found it the 

 smallest. One or other 

 carotid may be obliterated, 

 according, perhaps, as the 

 bird hal^itually sleeps with 

 the head under the right or 

 left wing. In the Apteryx 

 I found that the left caro- 

 tid alone passed to the usual 

 place in the neck, and di- 

 vided at the third cervical 

 vertebra to supply the head 

 in the usual way. In the 

 Flamingo the rio;ht carotid 

 was single and bifurcated 

 at the upper part of the 

 neck. In the Common 

 Fowl, each carotid, after 

 parting from the vertebral artery, ib. 6, proceeds to the middle 

 of the neck and soon disappears ; becoming covered by the muscles 

 of the anterior part of the neck, and entering the canal formed 

 by the hypapophyses, fig. 25, h, within which it lies hidden, and 

 in close contact with its fellow of the other side, to very near the 

 head. In the Bittern the two carotids are situated one behind 

 the other, and adhere so intimately together in this situation that 

 they seem like a single trunk. 



Arteries of the trunk. Grebe, sliv. 



