48 STUDIES IN COMPARATIVE ANATOMY. 



The mucous membrane of the mouth is in general smooth ; 

 that of the palate in particular is quite smooth, and shows none 

 of the transverse ridges which appear on the hard palate of the 

 horse and ox. Two shallow triangular depressions placed sym- 

 metrically immediately in front of the fore edge of the hard 

 palate lead to Jacobson's canals. The bony cavity in which the 

 canals lie runs in the suture between the premaxillse and 

 maxillae for 7 or 8 inches (Mayer gives 8 inches), taking a 

 nearly straight direction upwards and backwards ; it is furnished 

 with a vertical cartilaginous septum and a cartilaginous lining. 

 Each of the component canals is of about the diameter of a goose- 

 quill, and is lined by an extension of the mucous membrane of 

 the mouth. Camper (p. 48) says that these canals when pressed 

 exude a sticky fluid. 



Examination of skulls of different ages seems to show that 

 Jacobson's canals are at first nearly horizontal, but that as the 

 air-cells of the maxilla enlarge, the maxillo-premaxillary suture, 

 and with it the canals, is tilted more and more, until it 

 finally gets a steep slope forwards. 



Tongue. 



The tongue is thick and rounded towards its base, tapering and 

 pointed in front. Perrault describes it as 18 inches long, 

 but in our young example it was much shorter. The tip is 

 directed downwards, and lies almost invariably in the groove 

 formed by the low^er lip. All observation of the living animal 

 seems to show that the tongue, like the lips, is of little import- 

 ance in the act of feeding. The oral surface of the tongue ends 

 behind in a prominent concave edge, which forms the front and 

 lower boundary of the pharyngeal pouch. Towards the base are 

 two, four, or more circumvallate papillse of large size, while on 

 the side, especially behind, are a number of wart-like eminences 

 and mucous crypts. 



Salivary Glands, 



The parotid was small in our example, and measured only 

 4 inches by 3. Dr Watson gives 8 inches by 5 as the dimen- 

 sions. The gland is connected by a fibrous band with the 



