THE ETHMOID BONE. 33 



posteriorly, and with eleven bones of the face. It is 

 placed between the two orbits, and helps to form the 

 inner wall of each orbital cavity. It also assists in form- 

 ing the floor of the anterior fossa of the cranium and the 

 roof and sides of the nasal cavities. The vertical portion 

 of the ethmoid above the horizontal plate is a smooth, 

 triangular piece of bone with a sharp edge. It somewhat 

 resembles a cock's crest, and hence is called the crista 

 galli. Its sides are somewhat bulged, and it is frequently 

 hollow, inclosing a small air sinus. It serves for the 



FIG. 13. ETHMOID BONK. 



attachment of the falx cerebri. The vertical plate below 

 the horizontal portion is thin, quadrilateral in outline, 

 presenting the anterior superior and inferior borders, 

 the posterior superior and inferior borders, and two 

 surfaces. It assists in forming the septum of the nose, 

 and is generally slightly inclined to one side. It is some- 

 what roughened and grooved on its surfaces, and presents 

 many minute foramina near its junction with the hori- 

 zontal plate. The anterior superior border articulates 

 with the frontal and nasal. The triangular cartilage of 



