346 



THE MUSCULATURE 



Under the mucous membrane of the tongue is a dense layer of fibrous tissue, 

 the lingual fascia. In the body of the tongue there is a sagittal septum linguae, 

 which separates the two genio-glossus muscles. A transverse fibrous lamella, 

 the hyo-glossal membrane, helps to unite the tongue to the h3^oid bone. Delicate 

 membranes invest the free portions of the extrinsic muscles of the tongue. 



MUSCLES 



The stylo -glossus. — This arises from the front of the lower end of the styloid process of 

 the temporal bone and from the upper part of the stylo-mandibular ligament. Insertion. — It 

 runs obliquely downward, forward, and medially, with slightly diverging fibre-bundles, to the 

 lateral margin of the tongue, where it gives rise near the anterior pillar of the fauces to two 

 fasciculi. The larger, lateral, longitudinal fasciculus runs superficially along the lateral margin 

 of the tongue to the tip. The fibre-bundles are attached to the overlying mucosa and under- 

 lying musculature. The smaller, inferior, transverse fasciculus gives rise to diverging fibre- 

 bundles which pass medially through the hyo-glossus into the base of the tongue. The most 

 posterior of these diverging bundles may extend to the hyoid bone. 



The hyo-glossus. — This arises from — (1) the lateral part of the ventral surface of the body 

 of the hyoid bone and (2) from the upper border of the great cornu. The fibre-bundles take a 

 nearly parallel course upward, diverging, however, slightly. Near the upper margin of the back 



Fig. 349. — Side View of the Muscles of the Tongue. 



Lingualis inferior 



Genio-glossus -- 



Genio-hyoid 

 Anterior belly of 

 digastric 



Glosso-palatinus 

 Stylo-glossus 



Hyo-glossus 

 Mylo-hyoid 



part of the tongue they curve medianward and interlace with the intrinsic musculature of this 

 region. The dorsal fibre-bundles pass transversely, the middle obliquely, the ventral longi- 

 tudinally. They are inserted into the fibrous tissue which forms the skeletal framework of the 

 tongue. 



The chondro-glossus is a small muscle which arises from the lesser cornu of the hyoid bone 

 and gives rise to fasciculi which join the longitudinalis inferior and the longitudinalia superior 

 of the tongue described in Section IX. 



The genio-glossus. — This arises from the mental (genial) soine of the mandible partly 

 directly, partly by moans of a short, triangular tendon. The more inferior fibre-bundles radiate 

 toward the tip of the tongue; the intermediate extend directly toward the dorsum of the tongue, 

 where they are inserted into the lingual fascia and skeletal framework. The inferior curve 

 back to be inserted on the median part of the superior border of the hyoid bone. 



Nerve-supjdy. — Twigs from the hypoglossal nerve enter the lateral surfaces of the muscles 

 of this group. 



Action. — The chief of the muscles, the genio-glossus, performs various services according to 

 the part which contracts. The anterior portion .servos to withdraw the tongue into the mouth 

 and dcpres-s the tip; the middle portion to draw tho base of the tongue forward, depress the 

 median portion of tho tongue, and make the tongue jirotrudc! from the mouth; the inferior fibres 

 to elevate the hyoid l)one and carry it forward. The stylo-glossus retracts the tongue, elevates 

 its margin, and raises the hyoid heme and base of the tongue. Tho hyo-glossus draws down the 

 sides of the tongue and is also a retractor. The chondro-glossus aids in both these movements. 



Relations. — The main portion of the tongue is composed of the two genio-glossus muscles, 

 which are separated in the median lino by the lingual septum. The genio-gl()Ksus is covered 

 inferiorly by tho genio-hyoid and the mylo-hyoid muscles; along the lateral margin of the tongue 

 by the glos.so-palatinus, the stylo-glossus, the longitudinalis inferior, and the glosso-pharyngeus 



