42 



ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



To the outer side of the sella turcica we see the cerebral surface of the greater wing of the 

 sphenoid bone, which is separated from the overlying lesser wing of the sphenoid by the superior 

 orbital or sphenoidal fissure. The remaining boundaries of this surface are the same as those 

 seen on the external surface of the base of the skull, namely, the sphenoparietal and spheno- 

 squamosal sutures, the foramen lacerum or sphenopetrosal fissure. Near its origin from the 

 body, the greater wing of the sphenoid bone contains three orifices; the foramen rotundum, 



Fig. 45. — The inner surface of the base of the skull; the anterior fossa is colored blue, the middle fossa white, and the 



posterior fossa pink. 



directed obliquely anteriorly and leading into a short canal, the foramen ovale, and the foramen 

 spinosum. 



In addition to the greater wing of the sphenoid bone, the floor of the middle cranial fossa 

 is formed by the cerebral surface of the squamous portion of the temporal bone and by the an- 

 terior surface of the petrous portion, the posterior surface of the petrous portion and the mastoid 

 portion helping to form the floor of the posterior cranial fossa. The boundaries of the temporal 



