THE ORAL CAVITY. 437 



0-10-0-18 of a line in length, 0-02-0-04 of a line in breadth (extremes, 

 0-024-0-28 of a line in length, 0-004-0-05 of a line in 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 papillae, 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 frcena 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 movable 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 color, upon the alveolar processes ; where, united 

 into one mass with the proper mucous membrane and the periosteum, it 

 forms the gums ; upon the hard palate, to which the mucous membrane 

 is attached by an immovable thick fibrous layer, which in some parts 

 contains glands ; and finally upon the tongue, where the papillae are situ- 

 ated. In the latter case, there is a very close union between the mucous 

 membrane and the muscular tissue, the processes of many muscular 

 fibres extending into it and terminating especially in a white, very solid, 

 and dense, tendinous layer, which is in immediate contiguity with the 

 upper longitudinal muscular fibres, and has been described as the fascia 

 lingucB (Zaglas). 



With respect to the minute structure of the mucous membrane of the 

 mouth, connective tissue is the predominant constituent of the submu- 

 cous cellular tissue, while throughout the proper mucous membrane, very 

 numerous elastic elements are everywhere found. In both localities, the 

 former usually presents itself in bundles of 0-002-0-005 of a line in 

 breadth, not united into a network, but while they cross one another in 

 the most various directions, presenting a certain indistinct lamination. 

 The felted mass of connective fibrils becomes densest towards the epi- 

 thelium, and finally passes into a more structureless layer, which in my 

 opinion is here, as little as in the corium, to be considered a special mem- 

 brane.* In the interior of the papillce also, with the exception of those 

 of the tongue, a fibrous structure is usually very indistinct, the whole 

 more resembling a homogeneous substance, slightly granular. The 



* [This structureless layer is the " basement membrane" of Todd and Bowman, who 

 describe it as a separate membrane. DaC.] 



