.1Mr. Hunter observes that " there is a con s' erable degree of uniformity in the liver in this tribe of animals. In shape it nearly re sembles the human, but is not so thick at its base nor so sharp at the lower edge, and is probably not so firm in its texture. The right lobe (e, fig. 263) is the largest and thickest, its falciform ligament broad, and there is a large fissure (g) between the two lobes, in which the round ligament passes. The liver towards the left (f) is very much attached to the sto mach, the little epiploon being a thick sub stance. There is no gall-bladder." " The pancreas is a very long, flat body, having its left end attached to the right side of the first cavity of the stomach : it passes across the spine at the root of the mesentery, and near to the pylorus joins the hollow curve of the duodenum, along which it is continued, and adheres to the intestine, its duct entering that of the liver near the termination of the gut."— Phil. Trans. 1787, p. 410.
The structure of the biliary organs has a closer resemblance to that of Quadrupeds in the Herbivorous Cetacea, and differs from that above described in the presence of a gall bladder, besides some minor points.
In the Dugong the liver is a transversely oblong viscus, divided into three lobes with a fourth small process at the root of the left lobe, representing the lobulus Spigelii. It is as usual convex towards the diaphragm, but rather flattened than concave towards the viscera, the anterior margin thick and rounded. Of the .three larger lobes the middle one is the smallest, of a square shape, projecting forward, and as it were overhanging the gall-bladder, which is lodged in the middle of the inferior surface. The ligamentum suspensorium is continued upon the middle lobe, immediately above the gall-bladder, the anterior tnargin of this lobe being notched to receive it, and the remains of the umbilical vein entering the liver an inch above the fundus of the gall-bladder. The ti.vo lateral lobes are more than double the size of the cystic lobe, and of these the left is the largest. Both these lobes are concave to wards the small middle lobe, which they thus surround and conceal. The lobulus Spigelii is of a flattened and square shape, -measuring one inch and a quarter in length and one inch in breadth. The gall-bladder is of an elongated form, about an inch in diameter at the broadest part. It does not receive the bile by means of a communication between the cystic and hepatic ducts as in most animals, but that fluid is conveyed directly into it by two distinct hepato-cystic canals in the same manner and situation as the ureters terminate in the urinary bladder. The two orifices are half an inch apart on the same transverse line, and at a distance of three inches from the fundus vesicce they are large, readily admitting a full-sized probe. The common ducts, of which they are the terminations, are half an inch in length, and branch off into the lobes on either side. The inner membrane of
the gall-bladder is rugous ; it has a longer investment of peritoneum than in man. Where it ends it is difficult to say, as it gradually diminishes in size after the entry of the above ducts, and does not appear to be separated from the cystic duct by any marked contraction or valvular structure. The cystic duct is about six inches in length, and two lines in diameter; dilates a little before entering the duodenum, and as it passes between the coats of that intes tine the canal is provided with a reticular valvular structure of the inner membrane, which may probably supply the deficiency of this structure in the preceding parts of the duct.
Three vena cave hepatica from the three lobes of the liver join the vena cava inferior at the upper and posterior edge of the liver, which is not, however, perforated by it as in most quadrupeds. The vena porta, formed in the usual manner, but deriving a very small branch from the spleen, enters the fissure below the gall-bladder.
Sir Everard Home takes no notice of the pancreas ; Sir Stamford Raffles merely observes, that it lay ' below the duodenum.' It is situated below and behind the pyloric cavity of the stomach. Its length in a Dugong six feet long we found to be seven inches ; it was obtuse and thick at the splenic or left end, where its diameter i.vas two inches, and gradu ally growing smaller towards the duodenum, it terminated in one uncommonly large duct, which was three lines in _diameter and of great length. On laying open this canal the orifices of from twenty to thirty tributary ducts were observable, which were two lines in diameter; the coats of these ducts thick, and terminating in flattened lobules.
The spleen, as Sir S. Raffles observes, was very small, of a rounded form ; its length in the larger specimen four inches and a half, its breadth in the middle one inch and a half, from which it tapered to either end; its structure finely reticular.
In the Piked Whale the spleen is single and of small proportional size; in the Porpesse this organ is remarkable for its subdivision into distinct portions, of which one is generally about the size of a walnut (h, fig. 263); the others, to the number of four, five, or six (i, i), are of much smaller size.] The Spouting Whales always feed upon living food. The Dolphins and Cachalots pur sue or catch fish principally, and large Mollusks, whilst Whales prey upon the numerous little Molluscous and articulated animals and Vermes which swarm, it is said, in the northern seas, and in the number of which are reckoned crustaceans, cuttle-fishes, clios, medusas, sea anemonies, &c ; but in this respect a difference must be made between the Balcenopteraz and the Whales, properly so called (Balance), for we are assured that the first also feed upon fish, and are capable of swallowing much larger animals than the latter.