64 TOPOGRAPHICAL ANATOMY OF THE 



the larger branch — and, consequently, follows the lower border of the 

 hyoid bone in company with the external maxillary artery. It 

 passes medial to the hyo-glossal muscle and ends in the mucous 

 membrane of the posterior part of the tongue, where it is concerned in 

 the sense of taste. Filaments are furnished to the soft palate and the 

 tonsil, and a branch unites with a part of the lingual nerve. 



N. HYPOGLOSSUS. — Though a better opportunity for the examination 

 of the hypoglossal ^ or twelfth cerebral nerve will occur later, the 

 dissector should note certain features of its course before the parts are 

 further disturbed. In the present dissection the nerve appears between 

 the external carotid artery and the stylo-hyoid muscle. It follows the 

 lower border of the external maxillary artery as far as the origin of the 

 lingual, where it crosses the medial face of the external maxillary to 

 gain the surface of the hyo-glossal muscle. Continuing its course 

 medial to the mylo-hyoid muscle and parallel to the lower border of the 

 stylo-glossal muscle on the one hand and the submaxillary duct on the 

 other, it gains the substance of the tongue, to the muscles of which it 

 carries motor impulses. 



Dissection. — Reflect the stylo-glossal and hyo-glossal muscles. 



M. GENIOGLOSSUS. — The genio-glossal muscle is semi-penuiform and 

 flattened laterally. It lies against its fellow-muscle — from which it is 

 separated only by loose connective tissue containing a certain amount of 

 fat — and has a distinct tendinous lower border by which it is attached 

 to the symphysis of the mandible. The posterior part of the muscle is 

 fleshy and attached to the body and small cornu of the hyoid bone. 

 From its lower border the fibres of the muscle pass upwards in a 

 radiating manner to gain the substance of the tongue, some curving 

 forwards into the free portion of this organ. 



M. CERATOHYOIDEUS. — The cerato-hyoid is a small muscle consisting 

 of fibres running from the thyroid cornu of the hyoid bone to the small 

 and great cornua of the hyoid bone in the neighbourhood of their union. 

 A better view of the muscle will be obtained later. 



A. LiNGUALis. — The lingual artery has been followed to its dis- 

 appearance under the edge of the hyo-glossal muscle (page 60). Its 

 further course can now be examined. 



While under (medial to) the hyo-glossal muscle, the artery lies in 

 succession upon the cerato-hyoid muscle, the small cornu of the hyoid 

 bone, and the genio-glossal muscle. It is continued forwards to the tip 

 1 vird (hypo) [Gr.], under. yXQcrffa (glossa) [Gr.], the tongue. 



