462 MR. W. OTTLEY ON THE GROTJND-HORNBILL. [JlUie 3, 



and was kind enough to give me an injected specimen, the arteries of 

 which are described in this paper, in order to determine the question. 



The results of this examination show that, besides the possible 

 varieties in the arteries of the neck enumerated by Barkow in his 

 admirable paper in Meckel's 'Archiv' for 1829, there is a further 

 variety which he had not calculated upon. 



Meckel classifies these possible varieties in the following manner : — 



1. Both common carotids may runup the side of the neck. (Not yet 



observed.) 



2. One common carotid may be in the middle line and one on the 



side of the neck. 



a. The left superficial. 



b. The right superficial. (Not yet found.) 



3. Both may be in the middle line. 



a. The left covering the right. (Usual.) 



b. The right covering the left. 



4. They may unite in the middle line and divide again above. 



a. Both equal in size. (As iu the Common Bittern.) 



b. Left may be smaller. (As in Phcenicopterus, observed by 

 Garrod.) 



c. Right may be smaller. (As in Cacatua sulphurea, observed 

 by Meckel.) 



The variety which is met with in Bucorvus, however, is of a 

 different nature. Here there are two superficial arteries accompanying 

 the pneumogastric nerves, and they end above by anastomosing with 

 the vertebral arteries. But they are not carotid arteries ; for there 

 remain two fine cords, the obliterated common carotids, which are 

 attached below to the vertebral arteries, and which run inwards to 

 the middle line and continue up the neck in the hypapophysial canal, 

 covered over by fascia, but in no place by a bony arch. Opposite 

 the body of the fourth cervical vertebra both these fine cords leave 

 the canal, and, bending outwards beneath the oesophagus, end by 

 joining the vertebral arteries again very soon after these have turned 

 forwards, when they have escaped from their bony canal, and just 

 beyond the point where the internal carotid arteries are given off. 



The superficial arteries are then the enlarged representatives of 

 the anastomosing ascending and descending cervical arteries, which 

 usually are branches of the common carotid and superior thyroid 

 arteries respectively ; and their relatively large size is to be accounted 

 for by the obliteration of the common carotids. 



As a result of this arrangement of the vessels of the neck, the 

 origin of the arteries for the supply of the head differs from that 

 usually met with; and the second drawing shows the course of these 

 vessels, which hardly differed from one another on the two sides, 

 except as regards the size of one or two of the trunks. 



Description of the Vessels. 



The innominate arteries are given off from the aorta as usual ; and 

 after a short course upwards, across the bronchi, both arteries break 



