THE LINGUAL REGION. 



325 



stylo-mandibular ligament, to which its fibres, in most cases, are attached by a thin 

 aponeurosis. Passing downward and forward between the internal and external 

 carotid arteries, and becoming nearly horizontal in its direction, it divides upon 

 the side of the tongue into two portions : one longitudinal, which enters the side 

 of the tongue near its dorsal surface, blending with the fibres of the Lingualis in 

 front of the Hyo-glossus ; the other oblique, which overlaps the Hyo-glossus 

 muscle and decussates with its fibres. 



Relations. By its external surface, from above downward, with the parotid 

 gland, the Internal pterygoid muscle, the lingual nerve, and the mucous membrane 

 of the mouth ; by its internal surface, with the tonsil, the Superior constrictor, 

 and the Hyo-glossus muscle. 



The Palato-glossus, or Constrictor isthmi faucium, although it is one of the 

 muscles of the tongue, serving to draw its base upward during the act of degluti- 

 tion, is more nearly associated with the soft palate, both in its situation and func- 

 tion ; it will consequently be described with that group of muscles. 



Nerves. The Palato-glossus is probably innervated by the spinal accessory nerve, 

 through the pharyngeal plexus ; the remaining muscles of this group, by the hypo- 

 glossal. 



Muscular Substance of Tongue. The muscular fibres of the tongue run in vari- 

 ous directions. These fibres are divided into two sets Extrinsic and Intrinsic. 

 The extrinsic muscles of the tongue are those which have their origin external, 

 and only their terminal fibres contained in the substance of the organ. They are : 

 the Stylo-glossus, the Hyo-glossus, the Palato-glossus, the Genio-hyo-glossus, and 

 part of the Superior constrictor of the pharynx (Pharyngeo-glossus). The intrinsic 

 are those which are contained entirely within the tongue, and form the greater 

 part of its muscular structure. 



The tongue consists of symmetrical halves 

 separated from each other in the middle line by 

 a fibrous septum. Each half is composed of 

 muscular fibres arranged in various directions, 

 containing much interposed fat, and supplied by 

 vessels and nerves. 



CUT EDGE OF SUPERIOR LINGUALIS. 



FIG. 206. Muscles on the dorsum of the 

 tongue. 



FIG. 207. Coronal section of tongue. Showing intrinsic 

 muscles. (Altered from Krause.) a, lingual artery : b, Inferior 

 lingualis, cut through ; c, fibres of Hyo-glossus ; d, oblique fibres 

 of Stylo-glossus ; e, insertion of Transverse linguaiis ; /, Supe- 

 rior lingualis ; g, papillae to tongue ; h, vertical fibres of Genio- 

 hyo-glossus intersecting Transverse lingualis ; i, septum. 



To demonstrate the various fibres of the tongue, the organ should be sub- 

 jected to prolonged boiling, in order to soften the connective tissue; the dis- 



