GSO 





 CETOLOGY, 





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* 



Cetology. pressions from the vibrations of the atmosphere. They 

 N * "V""*' have a very large auditory canal, and a eustachian 

 tube of great diameter. Besides these, most species 

 possess a labyrinth with three semicircular canals, a 

 cochlea, a vestibule, and a tympanum lined with a 

 membrane, and provided with little bones articulated 

 together. The eustachian tube communicates inter- 

 nally by the tympanum with the mouth, and ascends 

 upwards towards the top of the spout-holes, into the 

 cavity of which it opens ; and that part of it which 

 is next the internal ear, exhibits, on its inner surface, 

 a pretty large hole, or empty depression. Both the 

 tube and its cavities are lined with a blackish delicate 

 mucous membrane. It is supposed by some, that 

 this organ assists the animal in receiving impressions 

 from odorous bodies. All the bony parts of the in- 

 ternal ear are exceedingly hard. 



The element in which these animals reside is well 

 calculated for communicating sonorous vibrations, 

 and it is probable that when they remain in their 

 usual position, with the head, or at least the external 

 auditory orifices, several feet below the surface of the 

 water, their hearing is much more acute than when 

 the head is elevated into the air. 



Seeing, The most perfect sensitive organ. in cetaceous ani- 



mals, is undoubtedly the eye ; for though this organ 

 is, in some species, extremely small in proportion to 

 the bulk of the animal, that of the largest whale 

 scarcely exceeding in .diameter the eye of a bull, yet 

 its conformation is as perfect as that of quadrupeds, 

 while it possesses, in common with that of fishes, a 

 peculiarity of structure, for the greater refraction of 

 the rays of light. 



We have already remarked (See ANATOMY, Part 

 II. vol. ii. p. 13 ) the unusual thickness and closely 

 interwoven fibres of the sclerotic coat of the eye in 

 these animals, and their want of lachrymal glands or 

 ducts. We may add, that the union between the 

 sclerotic coat and the cornea is much closer than in 

 quadrupeds, consisting of long and very delicate fila- 

 ments, that penetrate the substance of each membrane, 

 and fasten them together; that the fibrous and vascu- 

 lar structure of the choroid coat is extremely evi- 

 dent ; and that the crystalline lens, like that of fish- 

 es, is nearly spherical. 



D- tion. 



Mouth. 





Jaw 







SECT. III. Digestion. 



THE digestive organs of cetaceous animals differ 

 very considerably, according to the food on which 

 they live, and their manner of seizing it. Those of 

 mastication, in particular, are so various, as to consti- 

 tute the principal differences that discriminate the or- 

 ders and genera. 



The general form of the mouth is very different in 

 different species. In some, as the dolphin, and most 

 of its congeners, it is long, narrow, and shallow ; 

 while in others, as the proper whales and cachalots, it 

 is nearly of an oval form, and often extremely broad 

 and deep. The opening of the jaws in the baloence 

 and the cachalots is exceedingly wide, so as, in some 

 of the former, to admit of several men entering erect 

 the open mouth, and standing upright within the ca- 

 vity. 



The form and proportions of the jaws are very va- 

 rious. In soine v they are nearly of the same length ; 

 while in others, the lower jaw extends, beyond the up* 



per, or lies within it as in a groove. Sometimes the Cetology, 

 snout, formed by the anterior extremity of the jaws, ** -Y""" / 

 is pointed ; but in most cases it is more or less round 

 and obtuse. Teeth. 



In those CETACEA that have many terth in both 

 jaws, the teeth are so situated, as, when the jaws are PLATE 

 close, to lock into each other, They are most nu- CXXXIFI. 

 merous in the dolphin, in which some naturalists have ^'S' S ' 4 ' 

 reckoned above 180, while others saw only about 40 

 in both jaws, a difference which probably depends on 

 the age of the animal. They are almost always cy- 

 lindrical, or rather conical. Mr Hunter describes 

 them as composed of a double cone, one part of whick 

 extends beyond the gum, while the other constitutes 

 the fang by which they are inserted in the jaw. In 

 some species, as the dolphins, they are straight, and 

 more or less pointed ^ in others, as the cachalots, they 

 are usually curved and obtuse. 



The formation and progress of the teeth, in these 

 animals, appear to differ from those of quadrupeds. 

 They seem to be formed within the gum, and either 

 to sink thence into the sockets, or remain fixed till 

 these latter rise to inclose them. As in other ani- 

 mals, the number of the teeth seems to increase as 

 the jaws advance in length, though Mr Hunter is of 

 opinion, that they do not, like quadrupeds, shed their 

 teeth. Phil. Trans, vol. Ixxvii. p. 399. 



Most naturalists describe the body projecting from 

 the upper jaw of the narwhal as a tooth, though it pig. 5. 

 appears to us to have very little analogy to these or- 

 gans, and certainly does not assist in the process of 

 mastication. It is clearly a horn or tusk, similar to 

 those of the elephant and other quadrupeds, and is 

 calculated to serve the purposes of an offensive and 

 a defensive weapon. 



The balance, instead of teeth, have a curious ap- whale- 

 paratus, consisting of horny plates, with fringed or bone, 

 hairy borders hanging from the edge of the upper F'g- & 

 jaw. The description given of this substance by dif- 

 ferent naturalists, varies in several respects ; but the 

 most accurate account appears to be that of Cuvier, 

 which is as follows : 



The maxillary and palatine bones, in this tribe, 

 form on their inferior surface two inclined planes, 

 which give to the palate the appearance of the roof 

 of a house reversed, and their two surfaces are con* 

 cave. It is to those that the lamina? of the whale- 

 bone are attached: these are all parallel to each other, 

 and have a transverse direction with respect to the 

 axis of the body. Several hundred of laminae may 

 be counted on each side, and in the Greenland whale 

 they often exceed 10 feet in length. They are fixed 

 to the bone by a kind of fleshy or ligamentous sub- 

 stance. Each lamina presents, on its internal side, a 

 layer of horny fibres, growing from the horny plates, 

 but less fine, and more divided than the plates from 

 which they proceed. These fibres extend between 

 the plates, and form a fringe or loose border on the 

 lower part of the plates, so that these fringes hang, 

 down from every part of the palate, which is above 

 the tongue, and entirely invest this organ. The use 

 of this horny substance, or whalebone, seems to be 

 to retain, as with a net, those small animals which the 

 whales seize and swallow for food. Anat. Compar. 

 torn. iii. p. 199. 



The above description differs in several respects 

 from that of Mr John Hunter, in the Philosophical 





