2 SPECIAL HISTOLOGY. 



OF THE ORAL CAVITY. 



A. OP THE MUCOUS MEMBRANE OE THE ORAL CAVITY. 



§ 129. 



The commencement of the intestine may be said to have 

 only one tunic, the mucous membrane, which is applied more 

 or less closely to the bones and muscles bounding the oral 

 cavity; and is distinguished by its not inconsiderable thickness, 

 by its red colour, arising from the abundance of its vessels, and 

 by its numerous nerves and papillse. 



The proper mucous membrane, although it is continuous with, 

 and gradually passes into, the cutis upon the lips, is more trans- 

 parent and softer than the corium ; however, it possesses con- 

 siderable firmness and is still more extensible. Like the thinnest 

 portions of the cutis, it consists of a single layer, 0*1 — 0*2'" 

 in thickness, and presents a great number of papillse, like those 

 of the skin, upon its outer surface ; they are in general simple, 

 but occasionally bifnrcated (when hypertrophied they may pos- 

 sess even more processes), are conical or filiform, 0*10 — 018"' 

 in length, 002 — 004"' in breadth, (extremes, 0-024— 0-28'" 

 length, 0004 — 005'" breadth), and stand, without any very 

 regular distribution, so close together, that their bases are 

 almost in contact and are rarely more than their own breadth 

 apart. 



Besides these papillse, the mucous membrane presents upon 

 its free surface the orifice of the naso-palatine duct, and a 

 great number of glandular apertures, a few of which are 

 situated at the extremities of large papillary elevations. 



The submucous cellular tissue of the mouth varies in its 

 structure. On the floor of the oral cavity, on the anterior 

 surface of the epiglottis, and especially upon the fraena of 

 the lips, of the tongue, and of the epiglottis, it is thin and 

 yielding; and therefore, in these localities, the mucous membrane 

 is very moveable upon the subjacent parts. Where glands 

 occur in the submucous tissue, it is more solid, as in the lips 

 and cheeks ; at the root of the tongue, and on the soft palate, 

 it may be said to be firmly fixed, and here, especially in the 

 last-named localities, we find large masses of fat in it. The 

 submucous tissue is very dense, firm and of a whitish colour, 



