458 OF THE MOUTH. 



CHAPTER XIII. 



OF THE MOUTH. 



THE general cavity of the mouth is formed anteriorly and 

 laterally by the connexion of the lips and cheeks to the upper 

 and lower jaws ; so that the teeth and the alveoli of both jaws 

 may be considered as within the cavity. Above, it is bounded 

 principally by the palatine processes of the upper maxillary 

 and palate bones, and the soft palate, which continues back- 

 ward from them in the same direction. 



Below, the cavity is completed by several muscles, which 

 proceed from almost the whole internal circumference of the 

 lower jaw, and, by their connexions with each other, with the 

 tongue and the os hyoides, form a floor or bottom to it. The 

 tongue is particularly connected to this surface, and may be 

 considered as resting upon and supported by it. 



To acquire an idea of the parietes of this cavity, after 

 studying the upper and lower maxillary bones, the orbicularis 

 oris and the muscles connected with it, especially the buccina- 

 tor, ought to be examined ; and also the diagastricus, the 

 mylo-hyoideus, genio-hyoideus, and genio-hyoglossus. By 

 this it will appear that the lips and cheeks, and the basis or 

 floor of the mouth, are formed in a great measure by muscles. 

 Upon the internal surface of these muscles, a portion of cellular 

 and adipose substance is arranged, as well as glandular bodies 

 of different sizes ; and to these is attached the membrane which 

 lines the inside of the mouth. 



This membrane passes from the skin of the face to the lips, 

 and the inside of the mouth ; and, although it is really a con- 

 tinuation of the skin, there is so great a change of structure that 

 it ought to be considered as a different membrane. At the 

 orifice of the lips it is extremely thin, and so vascular, that it 



