416 



THE MUSCLES AND FASCIA. 



side; by its external surf ace, with the Inferior lingualis, the Hyo-glossus, the lin- 

 gual artery and hypoglossal nerve, the lingual nerve, and sublingual gland ; by 



its upper border, with the mucous membrane of 

 the floor of the mouth (frsenum linguse) ; 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 

 and whole length of the greater cornu of the hy- 

 oid bone, and passes almost vertically upward to 

 enter the side of the tongue, between the Stylo- 

 glossus and Lingualis. Those fibres of this mus- 

 cle which arise from the body (basio-glossus) are 

 directed upward and backward, overlapping 

 those arising from the greater cornu (kerato- 

 glossus), which are directed upward and forward. 

 Relations. By its external surface, with the 

 Digastric, the Stylo-hyoid, Stylo-glossus, and 

 Mylo-hyoid muscles, the submaxillary ganglion, 

 the lingual and hypoglossal nerves, Wharton's 

 duct, and the deep portion of the submaxillary 

 gland ; by its deep surface, with the Stylo-hyoid 

 ligament, the Genio-hyo-glossus, Lingualis, and 

 Middle constrictor, the lingual vessels, and the 

 glosso-pharyngeal nerve. 



The Chondro-glossus is a distinct muscular 

 slip, about three-quarters to an inch in length, 

 which arises from the inner side and base of the 

 lesser cornu of the hyoid bone and contiguous 

 portion of the body of the bone, and passes 

 directly upward to blend with the intrinsic mus- 

 cular fibres of the tongue, between the Hyo- 

 glossus and Genio-hyo-glossus. A small slip of 

 muscular fibre is occasionally found, arising from the cartilage triticea in the 

 thyro-hyoid ligament, and passing upward and forward to enter the tongue with 

 the hindermost fibres of the Hyo-glossus. 



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 apex, and from the 

 stylo-maxillary 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 Inferior lingualis, according to some authors, 

 by the chorda tympani ; the remaining muscles of this group, by the hypoglossal. 

 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. 



CHONDRO-GLOSSUS. 



FIG. 279. Muscles of the tongue from be- 

 low. (From a preparation in the Museum of 

 the Royal College of Surgeons of England.) 



