1885.] VISCERAL ANATOMY OF BIRDS. 843 



seen to be suspended in the middle of a horizontal septum [lassing 

 from side to side of ilie body ; the structure of this septum, however, 

 differs in different regions ; on the left-Iiand side of the body («) 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 con- 

 tinuous ill front with a kind of membranous diaphragm {d) which 

 shuts off the lobes of liver from the rest of the abdominal cavity : 

 this membrane bears a blood-vessel {J>) 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 nipnlensis) I have not found a close 

 similarity to Bvcorvus, and there are certain other features in the 

 anatomy of this genus which tend to remove it from other Hornbills '; 

 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 maxbnus 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 cctrbo 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-bbidder ', 

 which on account of its length recalls that of the Toucans ^ ; 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 se()tum. 



The horizontal septum is also present in Plectopterus gambensis, and 

 in Bernida brenta. A vertical septum immediately underlies the 

 sterna and median line of abdominal walls, and divides lobes i,f 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 sepaiable 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 Garrocl, Collected Papers, p. 316. 



- Figured by Watson, Report ou the Spheniscidje, Zool. Cball. Exp. v. xviii. 

 pi. xvi. fig. 9, pp. 1C>9, 19.5. 



^ See Forbes, Collected Papers, p. 323. 



