576 



CETACEA. 



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 diefundus vesica 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 cav<e 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 was 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 (A, fig. 263) ; the 

 others, to the number of four, five, or six (/, /), 

 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 Balanopterye and 

 the Whales, properly so called (Balterus), for 

 we are assured that the first also feed upon 

 fish, and are capable of swallowing much 

 larger animals than the latter. 



ORGANS OF CIRCULATION. The researches 

 of the anatomist on the circulating system of 

 the Cetaceans have not hitherto been extended 

 to many species. In its essential parts it is 

 similar to that in other Mammalia. But the 

 peculiar nature of Cetaceans, and the great 

 modifications of their organs of movement, 

 have necessarily produced in this system, not 

 only modifications analogous to those of these 

 organs, but vascular developments exclusively 

 characteristic of these animals. 



It is not known whether the Manatee pre- 

 sents anything particular in regard to the organs 

 of circulation, but the heart of the Dugong 

 (Jig- 264) and of the Rytina is cloven by the 



Fig. 264. 



Heart of the Dugong. 



deep separation of the two ventricles, .a cir- 

 cumstance which adds an important link of 

 affinity to those already subsisting between 

 these animals. 



y'n the heart of the Dugong, the ventricles, 

 ir Stamford Raffles has correctly described 

 them,* are not completely detached from one 

 another. The auricles are of equal size and 

 of a rounded form. In the right auricle (a), 

 which receives a single superior cava, the 

 coronary vein, and the inferior cava, there is 

 on the auricular side of the orifice of the 

 latter vein a fleshy Eustachian valve, of the 

 size and form which, in such cases, is com- 

 monly seen in the human subject. The valve 

 of the foramen ovale has a reticulate surface 

 at the upper margin, but is entire and im- 

 perforate. The right ventricle (b), in the Du- 



* Phil. Trtns. 1820, p. 174. 



