THE TONGUE 



347 



the mucous membrane called the foramen ccecum. From the 

 foramen caecum the two limbs of a V-shaped sulcus diverge 

 antero-laterally, to terminate on the margins of the tongue at 

 the attachments of the glosso-palatine arches. The V-shaped 

 sulcus is called the sulcus terminalis ; it is an indication of 

 the double origin of the tongue ; the part anterior to the 

 sulcus, which lies in the floor of the mouth, and is, therefore, 

 called the oral part ', is developed from the mandibular arches 

 and the associated tuberculum impar of the embryo ; the 



Tip of tongue, 

 turned up 



Deep lingual vein 



Orifice of. 

 submaxillary duct 



|::| ^Frenulum linguae 

 Plica fimbriata 



Plica sublingualis 



FIG. 130. The Sublingual Region in the interior of the mouth. 



posterior or pharyngeal part is developed from the second pair 

 of visceral arches. 



The mucous membrane of the pharyngeal surface lies in 

 relation with the soft palate and the posterior wall of the 

 pharynx, and it is continuous laterally with the mucous mem- 

 brane of the palatine tonsils, and, posteriorly, with that of the 

 epiglottis. Where it covers the pharyngeal surface of the 

 tongue it is smooth and glossy and it has no projecting papillae, 

 but it is studded with low elevations, produced by masses of 

 lymph follicles embedded in the submucous tissue, and in each 

 elevation there is usually a small central pit. As the mucous 

 membrane passes from the tongue to the epiglottis it is raised 

 into a small median fold called the glosso-epiglottic fold. 



