200 BONES OF THE FACE. 



alveolus of the central incisor has, according to Mr. Nasmyth, 

 the septum between it and its fellow twice as thick as that 

 of the other teeth; its antero-posterior diameter one-third 

 greater than at the sides, and its lateral diameter one third 

 greater in front than behind. Its anterior wall is so thin 

 as to be sometimes incomplete. 



The alveolus of the lateral incisor has less depth than the 

 central, its septum between the latter is not so thick as 

 between it and the canine, its posterior wall is thicker than 

 the anterior, and its antero-posterior diameter is greater 

 than the lateral. 



The alveolus of the canine ascends above the level of the 

 roof of the mouth, and is the deepest of all the alveoli ; 

 it corresponds to the anterior wall of the maxillary sinus, 

 is of oval form as the incisors, and has its antero-posterior 

 diameter about one tenth greater than the latter, and look- 

 ing backwards. 



The alveolus of the first bicuspid has its inferior part 

 partitioned into two cavities for the roots, the external 

 being the larger, while its middle is found narrowed. Its 

 depth is equal to the second bicuspid, but not so great as 

 the canine, and the septum between it and the latter is not 

 so great as that separating it from the second bicuspis. 



The alveolus of the second bicuspis is not narrowed in its 

 middle as the latter, nor divided by a middle septum into 

 cavities, and its form is oval. 



The alveolus of the first molar is divided into three cavi- 

 ties, two of which are external, the other internal ; the in- 

 ternal is the largest, and the posterior external the smallest, 

 hence a rule of practice for entering the antrum, founded 

 upon the size and direction of these cavities, always is to 

 select the internal or anterior external cavity for this pur- 

 pose; the internal cavity occasionally looks to a division of 

 itself, and is sometimes found to communicate with the pos- 

 terior, in which case only one root, strong and broad, is seen 

 instead of two. This alveolus is not unfrequently found to 

 open into the antrum, on which account it is regarded as 

 the most suitable one for perforating the antrum of High- 



