164 



HYO-GLOSSUS UNG-UALIS. 



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 

 Fi g- 72 -* 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 Al- 

 binus as two distinct muscles, 

 under the names of the basio- 



to 



glossus, and cerato-glossus, 

 which he added a third fasci- 

 culus, arising from the lesser 

 cornu, and spreading along the 

 side of the tongue, the chon- 

 dro-glossus. The basio-glossus 

 slightly overlaps the cerato- 

 glossus at its upper part, and is 

 separated from it by the trans- 

 verse portion of the stylo-glossus. 

 Relations. By its external 

 surface with the digastric mus- 

 cle, '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 con- 

 strictor of the pharynx, and 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 tongne, 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 relation by its under 

 surface with the ranine artery. 



* The styloid muscles 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 cxternus. 2, 2. The right side of the lower jaw, divided at its sym- 

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

 muscle. 5. The genio-hyo-glossus. 6. The hyo-glossus muscle ; its basio-glossus por- 

 tion. 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. 12. The os hyoides. 13. The thyro-hyoidean membrane. 

 14. The thyroid cartilage. 15. The thyro-hyoideus muscle arising from the oblique 

 line on the thyroid cartilage. 16. The cricoid cartilage. 17. The crico-thyroidean 

 membrane, through which the operation of laryngotomy is performed. 18. The 

 trachea. 19. The commencement of the oesophagus. 



