84 FORAMINA OF THE SPHENOIDAL BONE. 



the external plates the pterygoid muscles take their rise. At 

 the root of each internal plate, a small hollow may be remarked, 

 where the musculus circumflexus palati rises, and part of the 

 cartilaginous end of the Eustachian tube rests. At the lower 

 end of the plate is a hook-like process (hamulus) round which 

 the tendon of the last named muscle plays, as on a pulley. The 

 ossa palati, on each side, rest upon these internal plates ; and, 

 therefore, the pterygoid processes seem to support the whole 

 face. 



Foramina of the Sphenoidal Bone. 



Before these foramina are described, it is necessary to state, that the nerves of 

 the brain are named numerically, beginning with the olfactory, which is 

 foremost. 



It should also be observed, that each nerve of the fifth pair is divided, before it 

 passes from the cavity of the cranium, into three large branches. 



The first foramina are the optic, which have been already 

 described; they transmit the optic, or second pair of nerves, 

 and a small artery, to the ball of the eye. 



The second foramen, on each side, is the foramen lacerum. 

 It commences largely at the sella turcica, and extends laterally 

 a considerable distance, until it is a mere fissure. The upper 

 margin of this foramen is formed by the anterior clinoid 

 processes, and the edges of the smaller wings of the sphenoid 

 bone. This foramen transmits the third, fourth, and sixth pair 

 of nerves, and the first branch of the fifth pair, to the muscles, 

 and the other parts, subservient to the eye. 



The foramen rotundum, or third hole, is round ; as its name 

 imports. It is situated immediately under the foramen lacerum, 

 on each side, and transmits the second branch of the fifth pair 

 of nerves to the upper maxillary bone. 



The foramen ovale is the fourth hole. It is larger than the 

 foramen rotundum, and half an inch behind it. It transmits the 

 third branch of the fifth pair of nerves to the lower jaw. 



The fifth hole is the foramen spinale. It is small and round, 

 and placed in the point of the spinous process, behind the fora- 

 men ovale, to transmit the principal artery of the dura mater, 

 which makes its impression upon the parietal bone. 



