2 22 THE VISCERA. 



surface of the lip bears numerous large papillae. The lower 

 lip is also united to the jaw by a frenulum in the median line ; 

 it is again united to the jaw just caudad of the canine tooth, in 

 the space between the latter and the first premolar. Caudad 

 the two lips pass into each other (forming the commissura 

 labiorum), and unite with the cheek. The muscles of the lips 

 have been described (page 105). 



The cheeks (buccae) in the cat are comparatively thin and 

 small, extending from the lips caudad to the ramus of the 

 mandible. The outer surface is covered with hair; the inner 

 surface is smooth and somewhat folded. The buccal cavity is 

 rather small. On the inner surface of the cheek open the duct 

 of the parotid (Steno's duct), the ducts of the molar gland, and 

 that of the infraorbital gland. 



The roof of the mouth cavity is formed by the hard and 

 soft palates. The hard palate (palatum durum) forms the 

 cranial part of the roof; it is supported by the palatal plates of 

 the maxillary and palatine bones. The mucosa of the hard 

 palate is elevated to form seven or eight curved transverse 

 ridges, which are concave caudad. Between the ridges are 

 rows of papillai. In front of the most cranial ridge is a papilla 

 in the middle line, and at each side of the papilla is the open- 

 ing of a small duct (the incisive duct or Stenson's duct), 

 which leads dorsad through the incisive foramen to the 

 vomeronasal organ (or organ of Jacobson), which lies on the 

 floor of the nasal cavity. Caudad of the hard palate the roof 

 of the mouth is formed by the soft palate or velum palatinum, 

 described below. 



The floor of the mouth cavity is formed chiefly by the 

 tongue, which extends as far caudad as the isthmus faucium. 

 Ventrad of the free edge of the tongue the mucosa forms a 

 prominent median vertical fold which unites the tongue with 

 the floor of the mouth beneath it; this fold is the frenulum 

 linguae. On each side of the median line at the cranial border 

 of the floor of the mouth is a prominent papilla, at the apex of 

 which open the ducts of the submaxillary and sublingual 

 glands, the former on the lateral side of the apex, the latter 

 on the medial side. 



