MUSCLES OF THE TONGUE. 191 



Fourth Group. Muscles of the Tongue. 



Genio-hyo-glossus, Stylo-glossus, 



Hyo-glossus, Palato-glossus. 



Lingualis, 



These are already exposed by the preparation we have just made ; there 

 remains, therefore, only to dissect and examine them. 



The Genio-hyo-glossus, the first of these muscles, has been described 

 with the last group. 



The HYO-GLOSSUS is a square-shaped plane of muscle, arising from the 

 whole length of the great cornu and from the body of the os hyoides, and 

 inserted between the stylo-glossus and lingualis into the side of the tongue. 

 The direction of the fibres of that portion of the muscle which arises from 

 the body is obliquely backwards ; and that from the great cornu obliquely 

 forwards ; hence they are described by Albinus as two distinct muscles, 

 under the names of the basio-glossus, and cerato-glossus, to which he 

 added a third fasciculus, arising from the lesser cornu, and spreading 

 along the side of the tongue, the chondro-glossus. The basio-glossus 

 slightly overlaps the cerato-glossus at its upper part, and is separated from 

 it by the transverse portion of the stylo-glossus. 



Relations. By its external surface F ig< 



with the digastric muscle, the stylo- 

 hyoideus, stylo-glossus, and mylo- 

 hyoideus, with the gustatory nerve, the 

 hypoglossal nerve, Wharton's duct and 



the sublingual gland. By its internal 

 surface with the middle constrictor of 



',rfc 



the pharynx, the lingualis, the genio- 

 hyo-glossus, the lingual artery, and 

 the glosso-pharyngeal nerve. 



The LINGUALIS. The fibres of this 

 muscle may be seen towards the apex 

 of the tongue, issuing from the interval 

 between the hyo-glossus and genio- 

 hyo-glossus ; it is best examined by 

 removing the preceding muscle. It 

 consists of a small fasciculus of fibres, 

 running longitudinally from the base, 

 where it is attached to the os hyoides, 

 to the apex of the tongue. It is in re- 

 lation by its under surface with the ranine artery. 



* The styloid musc^s and the muscles of the tongue. 1. A portion of the temporal 

 bone of the left side of the skull, including the styloid and mastoid processes and the 

 meatus auditorius externus. 2, 2. The right side of the lower jaw, divided at its ym- 

 physis; the left side having been removed. 3. The tongue. 4. The genio-hyoideus 

 muscle. 5. The gemo-hyo-glossus. 6. The hyo-glossus muscle, its basio-glossus portion. 

 7 Its cerato-glossus portion. 8. The anterior fibres of the lingualis issuing from between 

 the hyo-glossus and genio-hyo-glossus. 9. The stylo-glossus muscle, with a small portion 

 of the stylo-maxillary ligament. 10. The stylo-hyoid. 11. The stylo-pharyngeus muscle 

 2. The os hyoides. 13. The thyro-hyoidean membrane. 14. The thyroid cartilage. 

 Jf S,' e th y r - hy ldeus muscle arising from the oblique line on the thyroid cartilage. 

 15. Ihe cncoid cartilage. 17. The crico-thyroidean membrane, through which the one- 

 ration of laryngotomy is performed. 18. The trachea. 19. The commencement oi th- 

 CD"ouhagus. 



r 



