CAVITY OF THE MOUTH. 197 



it ; the singular movements to be performed ; and the small 

 space left for the development of muscular fibre. When 

 all the muscles simultaneously contract the tongue is pro- 

 truded, as we cannot put out our own tongues without 

 being conscious of an effort. When the brevis alone con- 

 tracts, the tongue is drawn partially backward, though pro- 

 bably other muscles aid this action. 



The tongue is a double organ, and all of its muscles 

 except one exist in pairs. If the fibres of these muscles be 

 traced to their destination, they will be found to decussate ; 

 those of the right, terminating upon the left side of the 

 tongue. The muscles of the tongue consist of five pairs, 

 and a small single one. The genio hyo glossus (a pair) 

 lie immediately between the branches of the lower jaw 

 from the junction of which it proceeds in a direct line 

 to the spur process of the os hyoides. The insertion of its 

 fibres is into the top of the tongue. Hyo glossus longus 

 {a pair) arise by fine tendon from near the joint, formed 

 between the two horns of the os hyoides ; and extend to 

 the tip of the tongue, their muscular fibres being inserted 

 into the sides of the tongue. Hyo glossus brevis {a pair) 

 arise from the body of, and the spur process of the os hyoides ; 

 into the top of the tongue, extending from the velum 

 palati as far forward as the last molar tooth. Accessories 

 {two pairs) . The anterior springs from the large horn of the 

 OS hyoides, and blends with the anterior fibres of the brevis. 

 The posterior originates from the membrane upon the side 

 of the tongue, near its base ; and is inserted into the upper 

 and internal part of the brevis. The lingualis (single), a 

 small band of muscular fibre, originating from the most 

 forward part of the body of the os hyoides ; and is inserted 

 into the upper part of the tongue close to its root. 



The nerves which go to the tongue are the lingual, or 

 ninth pair for motion. The gustatory, or branch of the 

 fifth pair, which confers the sense of taste ; and the glosso 

 pharyngeus, of which the glossal branch goes to the tongue ; 

 but its precise service is not yet accurately determined. 

 We ask, may it not go to confer sensation? 



The arteries are derived from the submaxillary branch of 

 the carotids, and the blood is returned into the jugular. 



