BONES OF THE SKULL. 



125 



and fi 01 . 101 the external surface of the superior maxillary, 

 with the sixteen teeth, four incisors, Fig 102> 



two canine, and ten molars in situ. 



Fig. 102 exhibits the palate plates 

 of the superior maxillary (2), and the 

 palatine bones (3), together with 

 the arch formed by the sixteen teeth 

 (1, 1). 



[251. The lower jaw, in the adult, 

 is composed of a single bone ; in the 

 infant, it consists of two branches united along the median 

 line ; and this separation is permanent in a great many animals, 

 whilst in reptiles and fishes each branch consists of several 

 distinct bones united together. 



In man the lower jaw 

 (figs. 1 03 and 1 04) has some 

 resemblance to a horse shoe 

 with the branches bent up- 

 wards at an obtuse angle ; 

 it contains sixteen teeth, 

 and is articulated to the 

 glenoid cavity of the tem- 

 poral bone by a prominent 

 condyle (12) ; in front of 

 the condyle rises a second 

 eminence, called the coro- 

 noid process (14), serving for the attachment of the tem- 

 poral muscle. The elevatory muscles of the lower jaw 



Fig. 103. 



External surface. 



Fig. 104. 



are all attached near its 

 angle (3), they conse- 

 quently act at a short dis- 

 tance from the fulcrum, 

 the condyle (12), whilst 

 the resistance is situated at 

 a distance from the power; 

 the masseter and ptery- 

 goid muscles are fixed to the 

 inside as well as to the out- 

 side of the lower jaw ; 

 theyare fleshy and powerful, Internal surface. 



for the purpose of raising the jaw with force, for crushing 



