464 MR. W. OTTLEY ON THE GROUND-HORNBILL. [June 3, 



from the comes nervi vagi, 2, and which also furnishes several 

 branches to the syrinx and its muscles. And, lastly, the innominate 

 divides into subclavian and vertebral. From the former, S, only 

 one branch, the acromial thoracic, at, is seen to spring, before the 

 artery escapes from the thorax. The latter, V, soon sends a branch 

 downwards, D, which runs with the recurrent laryngeal nerve, and 

 ends by supplying the bronchus, the lung-substance, and the 

 oesophagus. The next branch, 2, is the comes nervi vagi, which 

 runs up the neck with the vagus nerve, and ends by anastomosing with 

 the vertebral. In its course it supplies : — (a) a branch to the thyroid 

 gland, Gl ; (b) a series of vessels forwards to the oesophagus, where 

 thev form loops and supply several branches to the trachea as well 

 as "to the skin ; (c) near the head a small offset to the internal 

 pterygoid muscle. After this the vertebral gives off a suprascapular 

 artery, Ss, and a superior intercostal (which from its lying behind 

 the vertebral cannot be represented) to the upper three spaces ; and 

 between these two and the branch 2 a white thin cord springs 

 from the inside of the vertebral, and, crossing, inwards beneath the 

 comes nervi vagi, gets beneath the oesophagus to the hypapophysial 

 canal. Here it is joined by its companion of the opposite side ; and 

 these cords run up the neck side by side till near the fourth cervical 

 vertebra, when they bend outwards, get from beneath the pharynx, 

 and end by joining the vertebral trunk (as seen in the second plan 

 of vessels), just after this artery has sent off that branch which 

 furnishes the internal carotid. 



It thus appears that the two true carotids are obliterated, while 

 their duty is performed by a superficial vessel on each side, which, 

 accompanying the vagus as it does, might be called the comes nervi 

 vagi, though by its position in the neck this vessel rather resembles 

 the true carotid of Mammalia. These vessels did not differ much in 

 size ; the right was somewhat larger ; but the vertebrals were almost 

 precisely symmetrical. 



As a result of this change in the vascular supply of the neck, the 

 arrangement of the vessels in the upper part of the neck and in the 

 head was a good deal modified. In the place of an anastomosis 

 betwean the vertebral and an occipital branch of the carotid, the 

 vertebral, which is large, turns forward and completes an arch with 

 the superficial comes nervi vagi, whose concavity is joined by the 

 obliterated carotid, while its convexity furnishes the branches for 

 the head. 



The following is a short description of their course and distribution 

 (vide fig. 2, p. 465). After the vertebral artery has turned forwards out of 

 the canal in the cervical transverse processes, its first branch ( 1 8) is dis- 

 tributed to the muscles attached to the back of the head. Another small 

 branch (11) is given downwards to reach the digastric and internal 

 pterygoid. A large vessel (10) then comes off, which soon enters 

 a bony canal behind the tympanum (the limits of which are marked 

 by the transverse lines in the plan), and divides into two (20, 2 1 ) ; the 

 upper vessel (20) turns behind the fenestra ovalis (F O), and, then 

 emerging from its canal, furnishes a large offset to the orbital plexus ; 



