DISSECTION OF THE HEAD AND NECK. 203 



the lingual nerves. Its posterior border is included between the mylo- 

 hyoid and the genio-hyoid muscles, and is related inferiorly to the sub- 

 mental artery. Its anterior border projects the mucous membrane at 

 the side of the tongue, so as to form the sublingual ridge. The upper 

 extremity is related to the lingual nerve and vein. It is a compound 

 racemose gland, and it discharges its secretion by from fifteen to twenty 

 ducts — the ducts of Rivinius — which perforate the little tubercles on the 

 sublingual ridge. 



Directions. — The gland is to be carefully excised without injury to 

 Wharton's duct or the adjacent vessels and nerves. It will be observed 

 to receive a nerve from the lingual branch of the 5th, while its vessels 

 are branches of the submental artery and vein. 



Wharton's Duct (Plates 30 and 31 and Fig. 23, 2 and 2') is the 

 excretory canal of the submaxillary gland. Leaving the lower ex- 

 tremity of the gland, where it is crossed outwardly by the submaxillary 

 artery, it passes between the mylo-hyoideus outwardly, and the great 

 hyo-glossus and the stylo-glossus muscles inwardly, its position here 

 being immediately behind the body of the hyoid. A little in advance 

 of the superior extremity of the sublingual gland it passes to its inner 

 side, and is continued downwards between the gland and the genio- 

 glossus muscle. Finally, it opens on the summit of the flattened papilla, 

 or barb, at the side of the freenum linguae. As the duct passes to the 

 inner side of the sublingual gland a branch of the lingual nerve turns 

 round it. The duct will be readily recognised and distinguished from 

 a blood-vessel by its slender and uniform calibre, and by its clear 

 contents. 



The Lingual or Gustatory Nerve is a branch of the 5th. It con- 

 tains here, however, not only its own proper fibres, but also fibres 

 derived from the 7th through the chorda tympani, which joins it in the 

 first part of its course. At the root of the tongue it passes between 

 the mylo-hyoideus and the stylo-glossus and great hyo-glossus muscles, 

 until it passes to the inner side of the sublingual gland. There it turns 

 forwards between the muscles, and is continued in a flexuous manner, 

 giving off branches that are distributed to the mucous membrane of 

 the tongue in its lower two-thirds. At the base of the tongue it de- 

 taches a few filaments to the mucous membrane there, to Wharton's 

 duct and the submaxillary gland, and a larger branch for the sublingual 

 gland and the adjacent mucous membrane. 



The Hypoglossal (12th) Nerve (Plate 30) will be found at the base 

 of the tongue, in front of Wharton's duct, where it is included between 

 the mylo-hyoid and great hyo-glossus muscles. Passing to the inner 

 side of the sublingual gland, it comes into relation with the lingual 

 nerve, and divides. The branches of the hypoglossal are motor to the 

 muscles of the tongue. 



