276 



THE ALIMENTARY TRACT, ETC. 



Fig. 178. 



F'« pi 



out : immediately within the lip is a deep, well-marked groove, the 

 outer boundary formed by the lip, the inner by a fold of the mucous 

 membrane (Fig. 178 /); this fold increases from behind forwards 

 as far as the premaxillary bones, where it forms two prominences 

 [F^, F^) with an interval between. These correspond to the 

 palatine processes of the premaxillary bones : immediately behind 

 them are openings of the dvicts of the intermaxillary glands. 



In the groove so foimed are 

 placed a single row of simple 

 teeth, which, though subject to 

 many variations, are usually 

 about fifty in number. 



A little further back and to 

 either side of the median line 

 is a small group of vomerine 

 teeth ( J'o) ; each group has from 

 live to ten teeth; external to 

 these is on each side a trans- 

 versely-placed oval opening, the 

 posterior nares [Clio). These 

 apertures are directed outwards 

 and backwards into a shal- 

 low groove, bounded anteriorly 

 by a fold of mucous mem- 

 brane. 



According to Wiedersheim the 



mucoiTs membrane immediately 



around the vomerine teeth is 



the epithelium surrounding these being 



Cho 

 ID 

 F 



The roof of the mouth. 

 Posterior naris. 



Opening of intermaxillary glands 

 Fold of mucous membrane. 



i^i, i^i Prominences of mucous membrane 



K 

 O 



S 

 .SI 

 T 

 Vo 



Muscles. 



Floor of the orbit. 



Lip. 



Lip. 



Eustachian tubes. 



Vomer. 



supplied with taste-bulbs 

 non-ciliated. 



The roof of the mouth iinderneath the parasphenoid is somewhat 

 vaulted and on either side depressed by the eyeballs, which project 

 downwards more or less prominently (0, 0). Still further back 

 are the openings of the Eustachian tubes (Fig. 178 T), one on 

 each side, and almost surrounded by the limbs of the pterygoid 

 bones. 



On the floor of the mouth (Fig. 179) the tongue [Z, Z'^) forms 

 the most prominent object ; its shape varying according to the state 

 of contraction of its muscles. Behind it, in the middle line, is a 

 transverse groove [■\), corresponding* to the posterior border of the 

 hyoid bone, and still further back is the oj)ening to the larynx [L), 



