Fontanelles : a, anterior 

 , posterior. 



Superior Maxilla 17 



to the finger and thumb the sensation of there being a parchment 

 patch in the skull-wall. 



There is a fontanelle at each angle of the parietal bone, as may be 

 seen on p. 366, but those at the sphenoidal 

 and mastoid angles are comparatively un- 

 important. In the case of tubercular inflam- 

 mation attacking the membranes of the brain 

 in a child before the fontanelle is closed, a 

 bulging may be found at that region. 



The superior maxilla is marked upon 

 the anterior surface by the ridge caused by 

 the fang of the canine tooth, which can be 

 felt even through the lip. Just external to 

 this is the canine fossa, from which the 

 levator anguli oris arises. Above the origin 

 to this muscle the infra-orbital nerve emerges 

 under cover of the levator labii superioris and of the orbicularis oris. 



The orbital surface articulates behind with the vertical part of the 

 palate, internally with the lachrymal and ethmoid. It is separated from 

 the great wing of the sphenoid by the spheno-maxillary fissure, which 

 ends externally in the vertical, pterygo-maxillary fissure. Thus the 

 hinder part of the jaw has no direct articulations. 



In a bony canal beneath the floor of the orbit run the infra-orbital 

 artery and the second division of the fifth nerve. 



The under surface of the palate process is rough, and at the 

 front it may be marked by a delicate articulation which runs outwards 

 and forwards from behind the anterior palatine canals to the interval 

 between the lateral incisor and canine teeth ; it shows the limit of the 

 inter-maxillary bone. This segment 

 has a separate centre of ossification, 

 and is developed in connection with 

 the vertical plate of the ethmoid 

 and the vomer. In extreme cases 

 of hare-lip the inter-maxillary bone 

 adheres to the tip of the nose. 



The antrum communicates with 

 the middle meatus by a small round 

 opening ; its inner wall is made up 

 by the vertical plate of the palate, 

 the lateral mass of the ethmoid, and 

 the inferior turbinated. The cavity 

 extends into the alveolar, malar, 

 and zygomatic parts of the bone, and is shut out from the orbit only 

 by a thin osseous plate. The roots of the first and second molar teeth 

 cause projections upon its inner wall. Abscess in the antrum may be 

 tapped by raising the lip and cheek in the neighbourhood of the canine 



c 



