Chap. XXIII.] 187 



CHAPTER XXIII. 



THE MOUTH, PHARYNX, AND TONGUE. 



250. The glaiids. Into the cavity of the 

 mouth and pharynx open very numerous minute 

 glands, which, as regards structure and secretion, are 

 either serous or mucous. The latter occur in the 

 depth of the mucous membrane covering the lips of the 

 mouth, in the buccal mucous membrane, in that of the 

 hard palate, and especially in that of the soft palate 

 and the uvula, in the depth of the mucous membrane 

 of the tonsils, at the back of the tongue, and in the 

 mucous membrane of the pharynx. The serous glands 

 are found in the back of the tongue, in close proximity 

 to the parts containing the special organs for the 

 perception of taste the taste goblets or buds (see 

 below.) All glands are of very minute size, but 

 when isolated they are perceptible to the unaided eye 

 as minute whitish specks, as big as a pin's head, or 

 bigger. The largest are in the lips, at the back of 

 the tongue and soft palate, where there is something 

 like a grouping of the alveoli around the small branches 

 of the duct, so as to form little lobules. 



251. The chief duct generally opens with a narrow 

 mouth on the free surface of the oral cavity ; it 

 passes in a vertical or oblique direction through the 

 superficial part of the mucous membrane. In the 

 deeper, looser part (submucous tissue) it branches 

 in two or more small ducts, which take up a number 

 of alveoli. Of course, on the number of minute ducts 

 and alveoli depends the size of the gland. 



In man, all ducts are lined with a single layer of 

 columnar epithelial cells, longer in the larger than 



