In the Porpesse the surface of the tongue is soft and smooth, and very flat superiorly ; the anterior margin is fringed by a number of short irregular processes (a, fig. 265).
The salivary glands are reduced to the most rudimental condition.
In the Phytophagous Cetaceans the stomach is separated into two portions (fig. 261); one, the cardiac (a), very large, the other, the pyloric (b), of narrower calibre, by a contrac tion (c) giving origin to two prolongations (d, d), which are tubiform in the Dugongs, and of a pouch-like form in the Manatees.
In both species there is a gland at the cardiac extremity of the stomach (c), which in the Dugong, Sir Everard Home (from whose memoir the figure subjoined is taken) describes as " forming a round mass, as in the Beaver. The orifices of these glands are small, and 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 : (f is the cesophagus, g the intestine.) The ccecum is simple and cordiform in the Dugong (fig. 262), but is of more irregular 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 ccecum, divided on its internal surface into numerous cells. A gland,remarkable for its size, is also found in the first portion of the stomach of this species. No sub stances butfuei 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 Phytophaga. In the Dolphins the teeth, which are generally simple and conical, or compressed in hnth inwc vary onn .1 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 cominerce), 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 Balvenidw. 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 larnin 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 rhynchus micropterus, the common Dolphin, the Small Bottle-nose ( Delphinus Tursio), the common Porpoise, the Grampus, the Phoctena globiceps, the carinated Porpoise, the Beluga, the Platanist, the Narwhal, the Great Bottle-nose or Hyperoodon, and the Piked Whale (Balecnoptera). There is no doubt that the stomachs of all these animals are very complicated ; and although it may be more than probable that they do not resemble each other in their composition, it is to be presumed, however, that it is to their complication we must attribute the essentially different descriptions which have been put forth on this subject.