136 THE SKULL. [chap. 



In accordance with the general form of the face the 

 mandible is short. The two rami of which it is originally 

 formed unite together at the symphysis within a year after 

 birth. They are widely divergent behind, and approach 

 in front at a much more obtuse angle than in the Dog. The 

 horizontal portion of each ramus is deep and compressed, 

 the lower margin straight or slightly concave, and produced 

 anteriorly rather in front of the alveolar margin, so as to 

 occasion the mental prominence, characteristic of the human 

 lower jaw. The anterior symphysial margin (Fig. 49, s), 

 therefore, instead of sloping upwards, from behind forwards, 

 is vertical, or rather inclined in the other direction. Pos- 

 teriorly, the condyle (cd) is more elevated than in the Dog, 

 and is less transversely extended. The coronoid process 

 (cp) is smaller and less recurved. The posterior border, 

 between the condyle and the angle (a), is nearly straight 

 and vertical, and the angle is rounded, compressed, slightly 

 everted, and not produced into any hook-like process, as in 

 the Dog. The depression for the masseter muscle is very 

 faintly marked. 



The hyoidean apparatus differs in several particulars from 

 that of the Dog. The tympanohyai can generally be 

 recognised in the skull of an infant at birth, and for a few 

 years after, as a cylindrical piece of bone, with a truncated 

 lower extremity, about one-twentieth of an inch in diameter, 

 seated in a depression in the hinder border of the tympanic, 

 immediately to the anterior and inner side of the stylo- 

 mastoid foramen. Its upper end becomes soon ankylosed 

 with the periotic. The tympanic is produced around it an- 

 teriorly, constituting the " vaginal process." The stylohyal 

 (s/i), at first a long styliform piece of cartilage, continuous 

 with the tympanohyai, commences to ossify by a separate 

 centre before birth, and, at a very variable period after- 



