LINGUAL REGION. 339 



Relations. By its internal surface, it is in contact with its fellow of the oppo- 

 site side, from which it is separated, at the back part of the tongue, by the 

 fibrous septum, which extends through the middle of the organ. By its external 

 surface, with the Lingualis, Hyo-glossus, and Stylo-glossus, the lingual artery 

 and hypoglossal nerve, the gustatory nerve, and sublingual gland. By its upper 

 border, with the mucous membrane of the floor of the mouth (frsenurn linguae). 

 By its lower border, with the Genio-hyoid. 



The Hyo-glossus is a thin, flat, quadrilateral muscle, which arises from the 

 side of the body, the lesser cornu, and whole length of the greater cornu of the 

 hyoid bone, and passing almost vertically upwards, is inserted into the side of 

 the tongue, between the Stylo-glossus and Lingualis. Those fibres of this 

 muscle which arise from the body, are directed upwards and backwards, over- 

 lapping those from the greater cornu, which are directed obliquely forwards. 

 Those from the lesser cornu extend forwards and outwards along the side of 

 the tongue, under cover of the portion arising from the body. 



The difference in the direction of the fibres of this muscle, and their separate 

 origin from different parts of the hyoid bone, led Albinus and other anatomists 

 to describe it as three muscles, under the names of the Basio-glossus, the 

 Kerato-glossus, and the Chondro-glossus. 



Relations. By its external surface, with the Digastric, the Stylo-hyoid, Stylo- 

 glossus, and Mylo-hyoid muscles, the gustatory and hypoglossal nerves, "Whar- 

 ton's duct, and the sublingual gland. By its deep surface, with the Genio- 

 hyo-glossus, Lingualis, and Middle Constrictor, the lingual vessels, and the 

 glosso-pharyngeal nerve. 



The Lingualis is a longitudinal band of muscular fibres, situated on the under 

 surface of the tongue, lying in the interval between the Hyo-glossus and the 

 Genio-hyo-glossus, and extending from the base to the apex of the organ. 

 Posteriorly, some of its fibres are lost in the base of the tongue, and others are 

 occasionally attached to the hyoid bone. It blends with the fibres of the 

 Stylo-glossus, in front of the Hyo-glossus, and is continued forwards as far 

 as the apex of the tongue. It is in relation, by its under surface, with the 

 ranine artery. 



The Stylo-glossus, the shortest and smallest of the three styloid muscles, arises 

 from the anterior and outer side of the styloid process, near its centre, and 

 from the stylo-maxillary ligament, to which its fibres, in most cases, are at- 

 tached by a thin aponeurosis. Passing downwards and forwards, so as to 

 become nearly horizontal in its direction, it divides upon the side of the tongue 

 into two portions ; one longitudinal, which is inserted along the side of the 

 tongue, 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 downwards, with the parotid 

 gland, the Internal Pterygoid muscle, the sublingual gland, the gustatory 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 upwards during the act of de- 

 glutition, is more nearly associated with the soft palate, both in its situation 

 and function ; it will, consequently, be described with that group of muscles. 



Nerves. The Palato-glossus is supplied by the palatine branches of Meckel's 

 ganglion; the Lingualis, by the chorda tympani; the remaining muscles of 

 this group, by the hypoglossal. 



Actions. The movements of the tongue, although numerous and complicated, 

 may be understood by carefully considering the direction of the fibres of its 

 muscles. The Genio-hyo-glossi, by means of their posterior and inferior fibres, 

 draw upwards the hyoid bone, bringing it and the base of the tongue forwards, 

 so as to protrude the apex from the mouth. The anterior fibres will draw the 



