464 STRUCTURE OF THE TONGUE. 



which are longitudinal ; 3d, of transverse muscular fibres, 

 reunited at the raphe, in the middle line of the tongue ; 4th, of 

 some vertical fibres which are inserted on the lower surface of 

 the mucous membrane. The ligament from the os hyoides 

 extended along the middle line of the tongue, Blandin calls the 

 lingual cartilage. The evidence in favor of its cartilaginous 

 nature, is not very satisfactory in man. The epidermis of the 

 tongue, which is much thicker than that of other portions of the 

 mouth, forms, according to Blandin, a sheath open at top, round 

 the sensitive papilla, which protects them when the tongue 

 acts as an instrument of mastication, and through which the 

 papillae protrude, to come fully in contact with the sapid sub- 

 stance when tumefied or erected by the gustatory excitement. 



In addition to these, are the extrinsic muscles, which origi- 

 nate from the neighboring parts, and are inserted and continued 

 into the substance of the tongue. See fig. 122. 



Among the most important of the muscles, are those which 

 proceed from the chin, or the genio-hyo-glossi. They are in 

 contact with each other ; their fibres radiate from a central 

 point on the inside of the chin, and are inserted into the middle 

 of the lower surface of the tongue : the insertion commencing 

 at a short distance from its apex, and continuing to its base. 



As the genio-hyo-glossi muscles have a considerable degree 

 of thickness, they add much to the bulk of the tongue in the 

 middle of the posterior parts of it. 



The hyo-glossi and the stylo-glossi, being continued into the 

 posterior and lateral parts, contribute also to the bulk of these 

 parts. 



The tongue, thus composed and connected, lies, when at 

 rest, on the mylo-hyoidei muscles ; and the space between it 

 and these muscles is divided into two lateral parts by the above 

 described genio-hyo-glossi. In the space above mentioned, is 

 a small salivary gland, of an irregular oval form ; the greatest 

 diameter of which extends from before backwards, and its 

 dges present outwards and inwards. It has several excretory 

 ducts, the orifices of which form a line on each side of the 

 tongue. This gland is very prominent under the tongue ; and 



