320 



THE MOUTH. 



FIG. 95. 



and these folds receive the name of frena or hridles of the 

 lips. Beneath the mucous layer of the lips are situated the 



labial glands. These consist of 

 small spheroidal granules. Like 

 the parotid and the rest of the 

 salivary glands, they lie close to 

 each other, but are distinct, and 

 have each a distinct excretory 

 duct, and open by a separate ori- 

 fice on the posterior surface of the 

 lips. Hence they are regarded as 

 true salivary, and not mucous 

 \ a glands, (Fig. 94.) 



The vascularity of the lips, as 

 shown under the microscope of 

 Mr. Nasmyth, is exhibited in 

 Fig. 95. A represents a part of 

 the mucous membrane on the in- 

 ner side of the upper lip of a 

 fetus, minutely injected, mag- 

 nified 40 diameters, a a Papilla?, 

 which become smaller towards the 

 middle of the figure, b Capilla- 

 ries forming a plexus with small 

 meshes, c The capillary plexus 

 coarser, the meshes larger and 

 corresponding to the situation of 

 the submucous glands. B also 

 magnified 40 diameters, repre- 

 sents a portion of the free edge of 

 the upper lip of a human foetus, 

 and shows the manner in which 

 the capillaries are arranged in the 

 papilla). 



The mucous membrane in pass- 

 ing from the lips over the alveolar 

 processes, to get behind the teeth, undergoes a most re- 

 markable and important change, being transformed into 

 the gums. 



