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Show 1885.] VISCERAL ANATOMY OF BIRDS. 843 seen to be suspended in the middle of a horizontal septum passing from side to side of the body ; the structure of this septum, however, differs in different regions ; on the left-hand side of the body (a) it forms a flat layer of unstriated muscular fibres connecting the gizzard with the oblique septum of that side of the body ; posteriorly and on the right side the membrane is thin and delicate, and is continuous in front with a kind of membranous diaphragm (cl) which shuts off the lobes of liver from the rest of the abdominal cavity : this membrane bears a blood-vessel (b) which evidently corresponds to the umbilical vein, and passes between the lobes of the liver along a median partition or umbilical ligament which separates them from each other. In other Hornbills (e.g. Aceros nipalensis) I have not found a close similarity to Bucorvus, and there are certain other features in the anatomy of this genus which tend to remove it from other Hornbills l; there is a well-marked umbilical ligament attached to the sternum, dividing the two lobes of the liver, and passing back as far as the end of the gizzard, but there is apparently no horizontal septum. The body-cavity of Larus maximus is separated into right and left halves by an umbilical ligament continuous from end to end, and a horizontal septum covers up all the abdominal viscera save the liver, and the gizzard, which projects through it. Phalacrocorax carbo has an identical arrangement. In the Penguin (Spheniscus demersus) the stomach lies rather nearer to the middle line than in birds generally ; indeed there are but few exceptions to the rule that the stomach lies on the left side of the abdominal cavity, as in the Crocodile, Tortoise, &c. Close to the stomach on the right-hand side is the elongated gall-bladder 2, which on account of its length recalls that of the Toucans 3 ; both viscera are suspended in a tough horizontal septum, which has the same relations as in the other birds already described. As in Bucorvus the lobes of the liver are shut off by a membrane from the abdominal cavity, each being, of course, in addition separated from the other by a partition, and thus enclosed in a cavity which is floored by a continuation of the horizontal septum. The horizontal septum is also present in Plectopterus gambensis, and in Bernicla brenta. A vertical septum immediately underlies the sterna and median line of abdominal walls, and divides lobes cf liver ; it starts from the pericardium in front, and is attached to middle line of sternum of abdominal wall as far back as the cloaca. This vertical septum is readily separable into two distinct superposed membranes, of which the left is attached close to the ventral median line of gizzard, while the right, which bears a conspicuous blood-vessel, is attached to the horizontal septum, which, as in the Stork & c , traverses the abdominal cavity, loosely covering the intestines and the posterior region of the gizzard ; anteriorly the horizontal septum is closely 1 Garrod, Collected Papers, p. 316. 2 Figured by Watson, Report on the Spheniscidae, Zool. Chall. Exp. v. xviii. pi. xvi. fig. 9, pp. 169, 195. 3 See Forbes, Collected Papers, p. 323. |
