Dissection of Sheep's Head. 231 



Hyoid arch. It will be seen to be in relation superiorly, 

 therefore, with the substance of the tongue : externally, with 

 the Stylo-glossus in its posterior moiety ; and the sublin- 

 gual gland and duct, and Whartonian duct in its anterior 

 moiety ; and lastly, to be crossed in its middle third by the 

 larger factor of the Hypo- glossal nerve. 



Thirdly will be seen an inferior stratum of longitudinal 

 fibres just internal to the raphe found between the Mylo- 

 hyoids : these are fibres of the Genio-hyoid muscle, arising 

 from the jaw near its symphysis and inserted into the Basi- 

 hyal (or *body ' of the hyoid bone). The Genio-hyoid may 

 be said to be between the Genio-hyo-glossus and the median 

 raphe of the Mylo-hyoid. 



The Hypo- glossal nerve will have been thus traced to take 

 the following course. After passing internal to the Digastric, 

 it proceeds beneath the Mylo-hyoid and inferior margin of 

 the Stylo- glossus, lying between it and the Hyo-glossus ; and 

 is then continued forwards along the external surface of the 

 Genio-hyo- glossus, which it finally penetrates, to reach the 

 tip of the tongue. 



At the same time a considerable part of the course of the 

 Lingual artery will have been made out ; arising from the ex- 

 ternal carotid artery as it crosses about the middle of the Stylo- 

 hyal bone, it continues in the direction of that bone across the 

 origin of the Stylo-glossus, dips down internal to the Hyo- 

 glossus, between it and the Genio-hyo-glossus (where it runs 

 parallel with the Hypo-glossal nerve), then ascending and 

 working forwards on the under surface as far as the tip of 

 the tongue under the name of the ranine* artery. 



The actions of the various muscles hitherto described may be 

 thus briefly stated. 



First Group. The Temporal, Masseter, and Internal Ptery- 



* Rana, a frog ; also a swelling under the tongue. 



