Chap. 5.] Sella ^urcica^ f?<v 103 



pterygoid proceftes rife from it ; thefe are extended to 

 join the ethmoid bone. The external furface of this 

 bone is every where covered with deprefiions, finuo- 

 fities, and foffe. Within there are three remarkable 

 folfej two of thefe are feated in the internal part of 

 each wing of the fphenoid bone, for receiving the mid- 

 dle part of the brain. The third, which is fmaller, is 

 feated on the top of the body of the bone, which fropa 

 its refemblance to a Turkifh faddle is defcribed under 

 the name of fella turcica. In this fofla a gland called 

 the pituitary is placed ; behind and before it are the 

 clinoid procefles. The holes on each fide of the os 

 fphenoides are fix proper and three common. The 

 firft is a round aperture, immediately below the anterior 

 clinoid precedes, which tranfmits the optic nerve and 

 ocular artery. The fecond, which is a large (lit, and 

 is called the foramen lacerum, tranfmits the third, 

 fourth, fixth, and the firft branch of the fifth pair of 

 nerves. The third hole, fituated a little lower, is called 

 rotundum from its fhape, and tranfmits the fecond 

 branch of the fifth pair of nerves. The fourth is the 

 foramen ovale, about half an inch behind the foramen 

 rotundum; through it paffes the third branch of the 

 fifth pair. Very near the point of the fpinous procels 

 is the fifth hole of this bone, which is fmall and round,- 

 and gives paflage to the largeft artery of the dura ma- 

 ter. The fixth proper hole cannot well be feen till ihe 

 cuneiform bone is removed from the other bones of 

 the cranium for one end of it is hid by a fmall pro- 

 tuberance of the internal plate of the pterygoid procels, 

 and by the point of the procefTus petrofus of the tem- 

 poral bone. Through it a eonfiderable branch of the 

 fifth pair of nerves is reflected. The firfl of the com- 

 mon apertures is that unequal fiffure at the fide of the 

 fella turcica, between the extreme point of the os pe- 

 H 4 trofum 



