28 A MANUAL OF DENTAL ANATOMY. 



its form, inasmuch as the two antra in the same individual 

 are sometimes quite dissimilar. The floor of the cavity is 

 rendered uneven in most specimens by prominences corre- 

 sponding to the roots of the molar teeth, which ordinarily 

 are but thinly covered by its bony walls, while it is not by 

 any means rare to find some of them actually bare. 



The cavity is also more or less completely subdivided by 

 bony partitions springing from its walls, as is well exempli- 

 fied in the accompanying figure ; these partitions are for 

 the most part thin, but they occasionally attain to consider- 

 able thickness, and they are stated to occur most frequently 

 at the anterior or posterior angles of the base of the 

 pyramid. 



On the base of the pyramid is the orifice by which it 

 opens into the middle meatus of the nose ; this orifice 

 being partly closed in by the ethmoid, palate, and inferior 

 turbinated bones, and also by soft parts, so that in a recent 



FIG. 13 0). 



subject it will barely admit a goosequill ; and it should be 

 noted that this orifice opens into the antrum near the top, 

 so that it does not afford a ready means of egress to fluids 

 accumulated in the cavity. 



Through this orifice the mucous membrane lining the 



(*) Section of an antrum of the left side, divided into many pouches, 

 by bony septa, and extending into the malar bone. Drawn from a 

 specimen in the collection of Dr. Maynard, in the possession of the Bal- 

 timore Dental College. 



