BO> T ES OF THE SKULL. 



125 



and fig. ]01 the external surface of the superior maxillary, 

 with the sixteen teeth, four incisors, Fig _ 102 _ 



two canine, and ten molars in situ. A ' ^ ' 



Fig. 102 exhibits the palate plates i AdliiM^ i 

 of the superior maxillary (2), and the . 

 palatine bones (3), together with f 

 the arch formed by the sixteen teeth 



[ 25 1 . 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 Fig- 103. 



(figs. 1 03 and 1 04) has some i^ 

 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 External surface> 



eminence, called the coro- 



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

 poral muscle. The elevatory muscles of the lower jaw 

 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 ; 

 they are fleshy and powerful, 



Internal surface. 



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



