THE MAXILLARY BONES. 29 



antrum is continuous with that of the nasal fossee, and, 

 like that, it is ciliated; but it differs from the latter in 

 being thinner and less vascular. 



The teeth which usually come into the closest relation 

 with the antrum are the first and second molars, but any of 

 the teeth situated in the maxillary bone may encroach upon 

 its walls, and I have seen an abscess, originating at the apex 

 of the fang of a lateral incisor, pass backwards and perforate 

 the antrum. 



Its walls have four aspects, namely, towards the orbit, 

 the nose, the zygomatic fossa, and the face, while its floor is 

 formed by the alveolar border. With the exception only of 

 the latter, its walls are very thin ; and this exception has 

 an important practical bearing in the diagnosis of tumors in 

 this region, as accumulations of fluid or morbid growths 

 really situated in the antrum bulge any or all of its walls 

 in preference to the alveolar border, whereas tumors spring- 

 ing from the base of the sphenoid or elsewhere and encroach- 

 ing upon the antrum, push down and distort the alveolar 

 border as easily as any of the other walls of the cavity, 

 inasmuch as the pressure caused by them is not transmitted 

 equally in all directions, as is the case when the medium 

 transmitting the power is a fluid. 



The lower maxilla or mandible consists of a body and 

 two rami, which ascend almost perpendicularly from its 

 posterior extremity. The horizontal portion or body is 

 curved somewhat in a parabolic form ; it has a convex ex- 

 ternal and concave internal surface, and an upper (alveolar) 

 and a lower border. On the convex facial surface we have 

 to note the ridge marking the position of the symphysis, 

 and below this the mental prominence. Externally to this, 

 below the line of contact of the first and second bicuspids 

 (or a little before or behind this point) is the mental fora- 

 men, which constitutes the termination of the inferior 

 dental canal. Running obliquely upwards, and first visible 



