INTERNAL SURFACE OF THE MOUTH. GUMS. 459 



produces the fine florid color which appears there in health. 

 It is covered by a cuticle, called by some anatomists, Epithe- 

 lium, which has a proportionate degree of delicacy, and carf be 

 separated like the cuticle in other parts. When this cuticle is 

 separated, the lips and the membrane of the mouth appear to 

 be covered with very fine villi, which are particularly apparent 

 in some preparations of the lips after injection and maceration.* 



Under this membrane are many small glandular bodies of a 

 roundish form, called glandulae labiales, whose excretory ducts 

 pass through it to the inner surface of the mouth, for the pur- 

 pose of lubrifying it with their secretion, which is mingled with 

 the saliva. 



The membrane which lines the inside of the lips and cheeks, 

 is somewhat different from that which forms the surface of the 

 orifice of the mouth : it is not so florid ; the blood-vessels in 

 its texture are larger, and not so numerous. This change, 

 however, takes place very gradually, in the progress of the 

 membrane, from the orifice of the lips to the back part of the 

 cheeks. Glandular bodies, like those of the lips, are situated 

 immediately exterior to this membrane of the cheeks, between 

 it and the muscles : their ducts open on its surface. These 

 glands are called Buccales. 



This lining membrane is continued from the internal surface 

 of the lips and cheeks to the alveolar portions of the upper and 

 lower jaws, which are in the cavity of the mouth, and covers 

 them, adhering firmly to the periosteum. 



The teeth appear to have passed through apertures in this 

 membrane, and are surrounded by it closely at their respective 

 necks. 



The portion of membrane, which thus invests the jaws, con- 

 stitutes the gums ; which have now acquired a texture very 

 different from that of the membrane from which they were 

 continued. They are extremely firm and dense, and very 

 vascular. It is probable that their ultimate structure is not 

 perfectly understood. 



* Ruysch had a fine preparation of this structure. See Thesaurus VII. Tab. 

 III. Fig. 5. 



