SECT. I29.] 



THE ORAL CAVITY. 



267 



(fig. 109), as, for instance, upon the gums, palate, the glandular 

 region of the root of the tongue, Fig. 109. 



the lips, and the lower surface of 

 the tongue. The nerves are di Hi- 

 cult to investigate. On the addi- 

 tion of caustic alkalies, a wide 

 network of finer and finest branches 

 is very obvious in the outer layers 

 of the mucous membrane, in which, 

 also, especially upon the anterior 

 surface of the epiglottis, divisions 

 of the nerve-fibres can be demon- 

 strated ; whilst, on the other hand, 

 it is frequently impossible to ob- 

 serve even a trace of nerves in the 

 papillce. In other cases, we per- 

 ceive also these, and especially in 

 the larger of them, one or two 

 nerve-fibres, often having a ser- 

 pentine course, o'002'", diminishing to o'ooi2'" in diameter, 

 without, however, being able to ascertain in what mode they end. 

 On the lips, although not in all individuals, the papillae contain 

 tact-corpuscles, like those of the papillae of the hand, only smaller. 

 I found here, likewise, Gerber's nerve-coils. As to the numerous 

 lymphatic vessels of the membrane of the oral cavity, but little 

 is known of their origin and relations in the mucous membrane 

 itself, still Sappey has injected networks of them in the gums and 

 hard palate (Anat. i. 2, p. 687, Ail. de Beau et Bonamy, t. iii., 

 pi. v., fig. 5). 



A simple papilla, with numerous vessels 

 (after Todd and Boicman) and epithelium, 

 from the gum of a child. Magnified 250 

 times. 



§ 129. The Epithelium of the Oral Cavity (fig. 109) is a lamel- 

 lated pavement epithelium, as it is termed, which consists of nu- 

 merous super-imposed, roundish, polygonal, in part flattened cells. 

 Considered as a whole, this epithelium is a transparent, whitish 

 membrane, on an average o'l'" to 02'" thick, of considerable 

 flexibility, but of slight elasticity and firmness, which can be 

 readily obtained in large connected patches by macerating or 

 scalding the mucous membrane, after the addition of acetic acid. 

 Its elements throughout are nucleated cells, which, in their 

 arrangement and structure, very much resemble those of the 

 epidermis \ yet they do not, like the latter, admit of being divided 

 into two sharply defined principal layers, but constitute a single 



