438 THE DIGESTIVE APPARATUS IN MAMMALIA. 



submaxillary gland, two faces, two borders, and two extremities, the relations 

 of which we will briefly indicate. 



The external face is covered by the mylo-hyoideus muscle ; the internal 

 responds to "Wharton's duct and the genio-glossus and great hyo-glossus muscles. 

 The upper border projects beneath the mucous membrane on the floor of the 

 mouth, where it forms the sublingual ridge ; the inferior, thin and sharp, is 

 comprised between the mylo-hyoideus and the genio-glossus muscles. The tivo 

 extremities are thin and tapering ; the posterior contains a branch of the Hngual 

 nerve ; the anterior extends to the bottom of the angle formed by the union of 

 the two branches of the inferior maxilla. 



Vessels and nerves. — This gland possesses a special, but small artery — the 

 sublingual. Its nerves come from the Ungual nerve, and even from the carotid 

 plexus. 



Excretory canals. — These number fifteen or twenty, and are named the ducts 

 of Rivinius. Flexuous and very slender, they are detached from the superior 

 border or internal face of the gland, ascend perpendicularly, and open into the 

 mouth on the sublingual crest or ridge, by a linear series of small orifices pierced, 

 as usual, in the centre of a tubercle. 



4. Molar Glands. 



These are so named, because they are disposed parallel to the molar arches. 

 There are two on each side. 



The superior molar gland — the most considerable — appears as a narrow line of 

 salivary lobules placed outside, and along the upper border of, the buccinator 

 muscle. In its posterior part, where it is concealed beneath the masseter muscle, 

 this gland is thicker and more compact than in front, where the few lobules 

 which compose it scarcely come in contact with each other. 



The inferior molar glajid — less lobulated and voluminous, and not so wide as 

 the preceding — is placed at the inferior border of the buccinator, immediately 

 beneath the mucous membrane of the mouth, and near the point where it is 

 reflected from the side of the cheek on to the inferior maxilla. It is bordered, 

 for the whole of its extent, by the buccal nerve. 



Both glands pour their secretion into the mouth by numerous salient orifices, 

 which can be seen arranged in line on the buccal membrane, parallel to each 

 molar arch. 



It may be remarked that these glands establish a transition between the 

 preceding and those yet to be mentioned. Their lobules are far from being so 

 compact as the parotid or sublingual lobules ; and they tend to separate from 

 each other, to become more independent. Therefore it is that many writers 

 regard them as distinct, and describe them as superior and inferior molar glands. 



5. Labial, Lingual, and Staphyline Glands. 



The lobules composing these glands are spread in layers, more or less thick, 

 on the inner face of the mucous membrane, instead of being agglomerated in 

 masses, as in the previous glands. Sometimes they are scattered, in consequence 

 of their small number. In general, the excretory duct of each glandule opens 

 independently into the mouth, without communicating with those of the neigh- 

 bouring lobules. 



Labial GlandulcB. — These are more abundant in the upper than in the lower 



