222 THE VISCERA. 
surface of the lip bears numerous large papille. 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 (bucce) 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 papillz. 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 
linguze. 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. 
