184 



its external border bends inwards to be attached to the anterior 

 cornu. 



6th. Tlie external cerato-maxillary (f) arises from the posterior 

 part of the ramus of the lower jaw, and becoming broader, is in- 

 serted into the anterior cornu of the os-hyoides. 



7\h. The middle cerato-maxillary (g) is narrow, and in part 

 concealed by the external. It extends from near the centre of the 

 ramus of the lower jaw straight backwards to be attached to the 

 outer extremity of the posterior cornu of the os-hyoides. 



8th, The internal cerato mamillary is long and slender (Fig. 1st, 

 2d, 6tli, h), and situated deep on the mucous membrane of the 

 mouth. It arises from the anterior part of the side of the lower jaw, 

 and passing thence backwards on the upper surface of the style and 

 muscles, ends in a tendon, which after uniting with its fellow of the 

 other side about two lines before the articulation of the cornu with 

 the body of the os hyoides, CFig. 1st. h) becomes broad, and is in- 

 serted into the roots of the posterior cornua. The last four muscles, 

 by contracting, will draw forwards the os hyoides, and protrude the 

 end of its style a short distance out of the mouth. 



9th. The hyo-glossus (Fig. 4. 6. iiii.) arises from the outer extre- 

 mity of the imosterior cornu of the os-hyoides. At first it accompa- 

 nies the cornu inwards to near the body, then leaves it, winds 

 round the cartilaginous pully on the anterior cornu, runs forwards 

 along the sides of the slyle and erectile portion of the tongue, and is 

 inserted into the anterior prehensile portion. This muscle admits of 

 remarkable elongation, as its extremities, which are not more than 

 an inch apart while the tongue rests in the mouth, become sepa- 

 rated during its complete protrusion to a distance of five or six 

 inches. It can only exert an action on the prehensile portion of the 

 organ, which it retracts into the mouth after having been protruded 



