CETACEA. 



573 



Fig. 261. 



Stomach of the Dugong. 



covered over with a membranous bag, which 

 has only one large aperture. The glandular 

 mass is divided into two portions."* Thus the 

 stomach of the Dugong presents peculiarities 

 which are met with singly in animals of the 

 Cetaceous, Pachydermatous, and Rodent Or- 

 ders. Like the stomach of the Whale it is 

 divided into distinct compartments ; like the 

 stomachs of the Hippopotamus and Peccary 

 it has ccecal pouches superadded to and com- 

 municating with it; and like those of the Dor- 

 mouse and Beaver its cardiac compartment is 

 provided with a glandular apparatus : (/is the 

 oesophagus, g the intestine.) 



The coecum is simple and cordiform in the 

 Dugong (fig. 262), but is of more irregular 



Fig. 262. 



Coecum of the Dugong . 



figure and bifurcated in the Manatee. The Ry- 

 tina appears also to possess a stomach divided 

 into two portions, of which the cardiac is also 

 larger than the pyloric ; and it has a very large 

 coecum, divided on its internal surface into 



* Phil. Trans. 1820, p. 317. 



numerous cells. A 

 gland,remarkablefor 

 its size, is also found 

 in the first portion of 

 the stomach of this 

 species. No sub- 

 stances but/tt' have 

 ever been found in 

 the alimentary canals 

 of these animals. 



The Zoophagous 

 Cetaceans present 

 still greater differ- 

 ences in their alimen- 

 tary organs than the 

 Pkytophaga. In the 

 Dolphins the teeth, 

 which are generally 

 simple and conical, 

 or compressed in 

 both jaws, vary con- 

 siderably in number, 

 and often remain concealed in a rudimen- 

 tary state in the gums. In the Cachalots 

 they are only found in the lower jaw ; are 

 simple and oviform ; and their number ap- 

 pears to be in no way certain. The Whales 

 have no true teeth, but at each side of their 

 palate grow, transversely, horny plates, named 

 baleen (the whalebone of commerce), pro- 



vided on their inner 



edges 



with fringe-like 



beards, amidst which, as in the meshes of a 

 net, the animals which form their food are 

 retained. 



[The structure, forms, and disposition of the 

 teeth having been given in the characters of 

 the different genera of Cetacea, we have here 

 only to add a few words on the subject of the 

 baleen-plates which form their substitutes in 

 the family of Balsenidae. Each of these plates 

 consists of a central, coarse, fibrous, and two 

 exterior or lateral compact layers; the first 

 extends beyond the latter, so that the plate 

 terminates at its lower or free extremity in a 

 fringe, and in looking upwards into the mouth 

 of a Whale when all the baleen-plates are in 

 situ, only their fringed extremities are seen. 



The base of each baleen-plate has a conical 

 cavity, which is fixed upon a pulp of a cor- 

 responding form, buried deeply in the firm 

 vascular substance of the gum which covers 

 the under surface of the maxillary and inter- 

 maxillary bones ; the sides of the base of the 

 baleen-plate are firmly attached to white horny 

 laminae of the gum, which are reflected from 

 one plate to another, and from which the ex- 

 ternal compact layers of the baleen are con- 

 tinued : the pulp appears to be subservient to 

 the secretion of the central coarse fibrous part 

 alone.] 



Nothing can differ more, or indeed be more 

 contradictory than the descriptions which have 

 been given of the stomachs of the Zoophagous 

 Cetaceans. In many of the species the struc- 

 ture of this part is unknown. It has been 

 more or less fully described in the Delphino- 

 rhynclius micropterus, the common Dolphin, 

 the Small Bottle-nose ( Dclphinus Tursio), 

 the common Porpoise, the Grampus, the 



