186 MUSCLES OF THE TONGUE. 



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 (yXuffira., 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 hypoglossal nerve. By its upper border with the mucous membrane 

 of the floor of the mouth, in the situation of the fraenum 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. 



The Genio-hyo-glossus, the first of these muscles, has been described 

 with the last group. 



The HYO-GLOSSUS is a square-shaped plane of muscle, arising from 

 the whole length of the great cornu and from the body of the os 

 hyoides, and inserted between the stylo-glossus and lingualis into the 

 side of the tongue. The direction of the fibres of that portion of the 

 muscle which arises from the body is obliquely backwards ; and that 

 from the great cornu obliquely forwards ; hence they are described by 

 Albinus as two distinct muscles, under the names of the basio-glossus, 

 and cerato-glossus, to which he added a third fasciculus, arising from 

 the lesser cornu, and spreading along the side of the tongue, the 

 chondro-glossus. The basio-glossus slightly overlaps the cerato- 

 glossus at its upper part, and is separated from it by the transverse 

 portion of the stylo-glossus. 



Relations. By its external surface with the digastric muscle, the 

 stylo-hyoideus, stylo-glossus and mylo-hyoideus, with the gustatory 

 nerve, the hypoglossal nerve, Wharton's duct and the sublingual gland. 

 By its internal surface with the middle constrictor of the pharynx, 



