1578 



HUMAN ANATOMY. 



The genio-hyoid (Fig. 1339) is a collection of fleshy fibres extending close to 

 the median line, from the inferior genial tubercle to the anterior surface of the body 

 of the hyoid bone. It is a thick band, four-sided on transverse section, with rounded 

 angles, and expands laterally on approaching its insertion. A layer of areolar tissue 

 separates it from its fellow. 



Nerve. The nerve-supply is from the hypoglossal, but probably consists of 

 fibres derived from the cervical nerves. 



Action. To draw the hyoid forward and upward ; or, when fixed below, to 

 depress the mandible. 



The genio-glossus (Fig. 1339) arises just above the preceding by short ten- 

 dinous fibres from the superior genial tubercle. Its inferior fibres run horizontally 

 backward to the base of the tongue, passing over the hyoid bone to the base of the 

 epiglottis ; the fibres above these, inserted successively into the mucous membrane of 



FIG. 1339. 



Stump of masseter 



Tensor 

 palati _ 



Levator 

 palati 



Hainuhir 



process Sty j oid proce ss 



Superior constrictor 



Pterygo-mandibular ligament 



Stylo-glossus 



Stylo-pharyngeus 

 Stylo-hyoid (cut) 



Hyoid bone 

 Thyro-hyoid 



Inferior constrictor 



Genio-hyoid Hyo-glossus 



Pharyngeal and extrinsic lingual muscles 



the dorsum of the tongue near the middle line, are at first oblique, then vertical, and 

 finally concave anteriorly as they approach the apex, so that the muscle is fan-shaped 

 when seen from the side. Each muscle is separated from its fellow by the median 

 septum. 



Nerve. The hypoglossal. 



Action. The complex action of this muscle includes retraction of the tongue by 

 the anterior fibres, drawing forward and protrusion by the posterior fibres, and depres- 

 sion, with increa.sed concavity, of the dorsum by its middle part. 



The hyo-glossus (Fig. 1339), external to the preceding, from which it is sepa- 

 rated by aicolar tissue, arisefl from the side of the body of the hyoid, the whole of the 

 greater horn, and the lesser horn. The last portion, rather distinct from the rest, is 

 de-M ritx-d sometimes separately as the chondro-glossus. The whole muscle, 

 applied to the side of the tongue, forms a layer of fibres directed upward and for- 



