THE LINGUAL REGION. 



323 



of the inferior dental ; its posterior belly, by the facial ; the Stylo-hyoid, by the 

 facial ; the Mylo-hyoid, by the mylo-hyoid branch of the inferior dental ; the Genio- 

 hyoid, by the hypoglossal. 



Actions. This group of muscles performs two very important actions. They 

 raise the hyoid bone, and with it the base of the tongue, during the act of degluti- 

 tion ; or, when the hyoid bone is fixed by its depressors and those of the larynx, 

 they depress the lower jaw. During the first act of deglutition, when the mass 

 is being driven from the mouth into the pharynx, the hyoid bone, and with it the 

 tongue, is carried upward and forward by the anterior belly of the Digastric, the 

 Mylo-hyoid, and Genio-hyoid muscles. In the second act, when the mass is pass- 

 ing through the pharynx, the direct elevation of the hyoid bone takes place by 

 the combined action of all the muscles ; and after the food has passed the hyoid 

 bone is carried upward and backward by the posterior belly of the Digastric and 

 Stylo-hyoid muscles, which assist in preventing the return of the morsel into the 

 mouth. 



4. Lingual Region. 



Genio-hyo-glossus. Stylo-glossus. 



Hyo-glossus. Palato-glossus. 



Chondro-glossus. 



Dissection. After completing the dissection of the preceding muscles, saw through the 

 lower jaw just external to the symphysis. Then draw the tongue forward, and attach it, by a 

 stitch, to the nose ; when its muscles, which are thus put on the stretch, may be examined. 



The Genio-hyo-glossus has received its name from its triple attachment to the 

 jaw, hyoid bone, and tongue, but it would be better named the Grenio-glossus, 



FIG. 204. Muscles of the tongue. Left side. 



since its attachment to the hyoid bone is very slight or altogether absent. It is a 

 flat, triangular muscle, placed vertically on either side of the middle line, its apex 



