ANATOMY IN A NUTSHELL. 525 



2. Crista galli is situated in the median line of the cribriform plate an- 

 teriorly. It is thick and triangular. The long border of this triangle, which 

 is the posterior one. gives attachment to the falx cerebri. The anterior border 



of this triangle, by its articulation with the frontal bone completes the foramen 

 caecum. Between the two laminae of this triangle, there may be a shuts. 



3. Grooves are on this plate on each side of the crista galli for the olfactory 

 bulbs. 



4. Foramina perforate this horizontal plate for the passage of the olfactory 

 nerves. These foramina are in three rows, (a) an inner row, which leads to the 

 nasal septum, (b) a middle row which leads to the roof of the nose, and (c) an 

 outer row which leads to the superior turbinated bone. 



5. Nasal slit is on the side of the crista galli anteriorly and is for the 

 passage of the nasal nerve, which is a branch of the fifth nerve. 



6. Triangular notch is at the back of the cribriform plate for the ethmoid 

 spine of the sphenoid. 



7. The perpendicular plate descends from the under surface of the 

 cribriform plate and assists to form the nasal septum. Its sides are grooved 

 for filaments of the olfactory nerves. The nasal spine of the frontal and crests 

 of the nasal bones articulate with its anterior border. The ethmoidal crest of 

 sphenoid articulates with the upper half of its posterior border, while the vomer 

 articulates with the lower half of this border. The triangular cartilage is at- 

 tached to its inferior border. 



The lateral masses of the ethmoid bone consist of a number of 

 cellular cavities, and each lateral half presents the following points 

 for consideration: 



1. The ethmoidal cells have thin walls and are situated between two 

 plates which form its sides. 



2. Os planum or orbital plate forms the outer surface of these cells and 

 also forms the inner wall of the orbit. It articulates with the orbital plateof 

 the frontal bone above, and forms the anteriorand posterior ethmoidal foramina 

 by their notched borders coming together with the superior maxillary bone 

 below, with the Lachrymal bone in front, and with the sphenoid and orbital 

 process of the palate bone behind. 



3. The middle turbinated process, which is concave outward andforms 

 part of the middle meatus, is the end of a thin plate of bone which descends 

 from the cribriform plate, and forms part of the outer wall of the nasal fossa. 



4. The superior turbinated process curves downward and outward. 



5. The UNCIFORM PROCESS passes downward to articulate with the in- 

 ferior turbinated bone and forms part of the inner wall of the antrum of High- 

 more. 



OSSIFICATION. It ossifies from three centers. One center for the body 

 and one for each lateral mass. 



Articulation. It articulates with thirteen bones, namely, the sphenoid 

 and frontal of the cranium, and all the bones of the face excepl the two malar 



and the inferior maxillary. The bones of the face it articulates with are: the 

 two nasal, two superior maxillary, two lachrymal, two palate, two inferior tur- 



