42 PRACTICAL ANATOMY. 



posterior and anterior dental canals, these are seen to 

 run in the outer wall of the antrum, skirting its lower 

 portion. Running in the roof of the maxillary sinus is 

 the infra-orbital canal, the floor of which is quite thin.* 

 At the junction of the internal with the superior sur- 

 faces are a series of broken cells. Below the antrum 

 the bone is smooth, concave, and continuous with the 

 superior surface of the palatine process. Running from 

 the lower portion of the opening of the antrum down- 

 ward and forward is a fissure for articulation with the 

 maxillary process of the palate bone. Posterior to the 

 antrum the inner surface is rough, and articulates with 

 the external surface of the vertical portion of the palate, 

 which converts a groove on the inner surface of the 

 superior maxillary into a canal, the posterior palatine ; 

 it passes downward and slightly forward, and transmits 

 the posterior palatine nerve from Meckel's ganglion. At 

 the anterior portion of the inner surface is a trilateral plate 

 of bone, the nasal process, about one and one-half inches in 

 length and three-fourths inch in width. At its upper por- 

 tion is a ridge called the superior turbinated crest, and at 

 its lower portion another ridge, the inferior turbinated 

 crest, which articulate with the middle turbinated process 

 of the ethmoid and the inferior turbinated bone, respect- 

 ively. Behind the nasal process, between it and the 

 antrum, is a deep groove, the lachrymal, which is con- 

 verted into a canal by articulation with the lachrymal 

 and inferior turbinated. It lodges the nasal or lachrymal 

 duct, and terminates in the inferior meatus of the nose. 

 All that portion of the inner surface of the nasal process 

 between the superior and inferior turbinated crests enters 

 into the formation of the middle meatus of the nose. 



* A study of the position of this canal is important in excision of the 

 second division of the fifth nerve by Garretson's operation. 



