Edges. 



20 DESCRIPTION OF THE SKELETON. 



of the infra-maxillary canal, which is twelve inches long, and one and three 

 quarters in diameter. Below and behind the infra-maxillary orifice is an 

 extremely rough surface, nearly fourteen inches in its longest diameter, for 

 the attachment of the internal pterygoid muscle. On the inner surface 

 below the neck is a rising for the attachment of the external pterygoid 

 muscle. 



The internal face of the body of the bone is oblique from above down- 

 wards, and from within outwards, except at its anterior part, where the 

 direction of this face becomes perpendicular ; and there it terminates in 

 the infra-maxillary symphysis and gutter. The latter extends from the 

 lower edge of the symphysis, first upwards, then forwards, and at last down- 

 wards, where it terminates in the anterior edge of the body of the bone. 

 This groove, destined to receive the anterior extremity of the tongue, is about 

 twelve inches long, and three and a half in its greatest width. The bone 

 terminates anteriorly in a truncated manner ; the truncated portion, having 

 a circular form, is about three inches in diameter. In this portion we 

 perceive on the left side the incisor tooth, or tusk (Large Plate) ; on the 

 right side exists a depression an inch and a half deep, which had formerly 

 contained a corresponding tusk. The depth of the cavity on the left side 

 is seven inches. 



The superior edge of the body of the bone behind, where it joins with 

 the branch, has a slight fossa, the posterior part of which is a canal for 

 the vessels and nerves. Immediately behind the molar teeth is a small 

 ridge, which gradually separates into two, forming the external and internal 

 alveolar ridges. In front of the molar teeth, these ridges unite together, 

 and are two inches thick at their point of union. They gradually coalesce 

 into a single ridge, which extends forwards to terminate over the tusk- 



