80 OS SPHENOIDES. 



Os Sj)henoides. 



The OS sphenoides or ptcrygoideus, resembles a bat with its 

 wings extended. It consists, 



1st. Of a body with two processes arising from it, called the 

 lesser tvings, or apophyses of Ingrassias. 



2dly. Of two large lateral processes, called the greater wings, 

 or temporal processes ; and, 



3dly. Of two vertical portions, denominated pterygoid pro- 

 cesses. 



The body is situated near the centre of the cranium, and in 

 contact with the cuneiform process of the occipital bone ; the 

 greater wings extend laterally between the frontal and temporal 

 bones as high as the parietal ; while the pterygoid processes 

 pass downwards on each side of the posterior opening of the 

 nose, as low as the roof of the mouth. It is, therefore, in 

 contact with all the other bones of the cranium, and with many- 

 bones of the face. 



The body has a cubic figure ; its upper surface forms a portion 

 of the basis of the cranium ; its lower and anterior surfaces form 



Explanation of the Figures in the Plate referred to above. 

 FIG. I. 

 Represents the upper surface, or cribriform plate of the Ethmoid Bone. 

 a. Crista Gain. 

 b b b b. Cribriform plate. 



c. Surface denominated Os Planum. r 



d d. Hollow Triangular Pyramids. 



e. Space between the Pyramids for receiving the Azygos Process of the Os 

 Sphenoides. 



FIG. II. 

 A lateral View of the Bone. 

 a. Crista Galli. 



c. Os Planum. 



d. Triangular Pyramid. 



FIG. III. 

 The Bone Inverted. 

 a. The Nasal Plate of the Ethmoid Bone, which constitutes the upper portion 



of the Septum of the nose. 

 g g. Those portions of the Ethmoid which are called Superior Turbinated 



Bones. 

 //. The Cellular Lateral Portions of the Bone, 

 d d. The Triangular Pyramids. 



e. Space between the Pyramids for the Azygos Process of the Os Sphenoides 

 — a foramen on the internal side of one of the Pyramids. 



