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Show 462 MR. W. OTTLEY ON THE GROUND-HORNBILL. [J and was kind enough to give m e 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 lurther 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.) 6. The right covering the left. 4. They may unite in the middle line and divide again above. a. Both equal in size. (As in 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 wbere 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 |