32 



ON THE FOEM AND SIZE 



extending across tlie antrum." It would be 

 difficult to describe every variety of form and 

 size wliicli may be seen in the human antrum 

 at adult age, and such knowledge can only be 

 obtained by the personal examination of nume- 

 rous specimens. As a general rule, it is larger 

 in the male than in the female, and perhaps 

 diminishes in size with extreme age. It is lined 

 by a muco-serous membrane, which, in the healthy 

 state, allows air to enter the sinus through an 

 opening in the upper part of the posterior wall. 

 In the young subject the cavity is small, and its 

 walls comparatively thick. The roots of the 

 molar and bicuspid teeth, if fully developed, often 

 perforate the floor, but more frequently they are 

 covered by a very thin layer of the inferior wall. 

 The specimens (Figs. 3, 4, 5) have been selected 

 from a hundred bones taken indiscriminately. 



Fig. 3. 



Common shape and size of the Adult Antrum, capable of containing 2.J drams of fluid 

 {transverse section). 



