MUSCLES OF THE TONGUE. 493 



which may be known by its darker colour, and by its transpa- 

 rency. 



The muscles of mastication being the Temporalis, the Mas- 

 seter, the Pterygoideus Intern us, and the Pterygoideus Exter- 

 nus, their description may be seen elsewhere. 



CHAPTER III, 



OF THE TONGUE. 



THE Tongue (Lingua) is the principal organ of taste, and is 

 also concerned in mastication and in speech. It is an oblong, 

 flattened, symmetrical, muscular body, which extends from the 

 os hyoides posteriorly to the incisor teeth anteriorly, and, being 

 placed at the bottom of the mouth, fills up the space within the 

 two sides of the body of the lower jaw. The exact extent of room 

 which it occupies, varies according to its being in a state of re- 

 pose or. of activity. 



The posterior extremity of the tongue is called its base or 

 root, and arises muscular from the body and the cornua of the 

 os hyoides; it is there considerably thinner than elsewhere, it also 

 has a fibro-muscular origin from the centre of the epiglottis car- 

 tilage: sometimes a cartilage is found in the middle of the base, 

 and which forms a sort of ball and socket joint with the os hy- 

 oides. Its anterior extremity is called the tip or point, is loose, 

 and has a rounded thin termination. Between the point and 

 the base is the body. The superior surface of the tongue is flat, 

 is divided by a middle longitudinal fissure of inconsiderable 

 depth into two equal parts, and is covered by the lining mem- 

 brane of the mouth, under a particular modification of structure. 

 The inferior surface of the tongue, with the exception of its 

 middle part, is also free, and covered by the common mucous 

 membrane of the mouth; but the latter is there very thin, and the 

 veins may be readily seen shining through it. 



SECT. I. MUSCLES OF THE TONGUE, 



The muscles which compose the principal part of the bulk of 

 the tongue, are, the Stylo-glossus, the Hyo-glossus, the Genio- 

 VOL. I. 42 



