MUSCLES OF THE TONGUE. 163 



surface, with the genio-hyoideus, the genio-hyo-glossus, the hyo- 

 glossus, the stylo-glossus, the gustatory nerve, the hypo-glossal 

 nerve, Wharton's duct, the sublingual gland, and the mucous mem- 

 brane of the floor of the mouth. 



After the mylo-hyoideus has been examined, it should be cut 

 away from its origin and insertion, and completely removed. The 

 view of the next muscles would also be greatly improved by 

 dividing the lower jaw a little to one side of the symphysis, and 

 drawing it outwards, or by removing it altogether if the ramus 

 have been already cut across in dissecting the internal pterygoid 

 muscle. The tongue may then be drawn out of the mouth by 

 means of a hook. 



The genio-hyoideus (ys'vsiov, the chin) arises from a small tubercle 

 upon the inner side of the symphysis of the lower jaw, and is inserted 

 into the upper part of the body of the os hyoides. It is a short and 

 slender muscle, very closely connected with the border of the fol- 

 lowing. 



Relations. By its superficial or inferior surface, with the mylo- 

 hyoideus ; by the deep or superior surface with the lower border of 

 the genio-hyo-glossus. 



The genio-hyo-glossus (yXuctfa, the tongue) is a triangular muscle, 

 narrow and pointed at its origin from the lower jaw, broad and 

 fan-shaped at its attachment to the tongue. It arises from a 

 tubercle immediately above that of the genio-hyoideus, and spreads 

 out to be inserted into the whole length of the tongue, from its base 

 to the apex, and into the body of the os hyoides. 



Relations. By its inner surface with its fellow of the opposite 

 side. By its outer surface with the mylo-hyoideus, the hyo-glossus, 

 the stylo-glossus, lingualis, the sublingual gland, the lingual artery 

 and the hypo-glossal nerve. By its upper border with the mucous 

 membrane of the floor of the mouth, by the side of the frsenum 

 linguae ; and by the lower border with the genio-hyoideus. 



Actions. The whole of this group of muscles acts upon the os 

 hyoides, when the lower jaw is closed, and upon the lower jaw 

 when the os hyoides is drawn downwards, and fixed by the 

 depressors of the os hyoides and larynx. The genio-hyo-glossus is, 

 moreover, a muscle of the tongue ; its action upon that organ shall 

 be considered with the next group. 



Fourth Group. Muscles of the Tongue. 



Genio-hyo-glossus, 



Hyo-glossus, 



Lingualis, 



Stylo-glossus, 



Palato-glossus. 



These are already exposed by the preparation we have just 

 made ; there remains, therefore, only to dissect and examine them. 



