THE BONES OF THE HEAD 87 



the internal pterygoid plate, or to the pterygoid fossa external to 

 the scaphoid fossa. It transmits a small emissary vein from the 

 cavernous sinus. Behind and external to the foramen ovale is the 

 small circular foramen spinosum, close to the spinous process, which 

 opens vertically downwards. It transmits the middle meningeal 

 artery and a recurrent branch of the inferior maxillary nerve, 

 and is sometimes incomplete posteriorly. Internal to this foramen, 

 between it and the foramen ovale, there is sometimes a small 

 opening, called the canaliculus innominatus, for the small superficial 

 petrosal nerve. 



The antero -internal surface is divisible into a large orbital portion 

 and a small spheno-maxillary portion. The orbital division is 

 quadrilateral, smooth, and slightly concave, and it forms the greater 

 part of the outer wall of the orbit. The spheno-maxillarv division 

 is situated at the lower and inner part above the root of the 

 pterygoid process. It is pierced by the foramen rotundmn, and 

 lies in the posterior wall of the spheno-majcillary fossa. 



The external or iemporo-zygomatic surface is elongated from above 

 downwards, and is continuous with the outer surface of the external 

 pterygoid plate of the pterygoid process. Towards its lower part it is 

 crossed by the infratemporal crest, which divides it into a large 

 upper and a small lower portion. The upper or temporal division, 

 which is directed outwards, forms part of the temporal fossa, and 

 gives origin to fibres of the temporal muscle. The lower or 

 zygomatic division looks dowTiwards into the zygomatic fossa, and 

 gives origin to the upper head of the external pterygoid muscle. 

 At its lower and back part it presents the openings of the foramen 

 ovale and foramsn spinosum. 



The posterior border extends from the spinous process to the body, 

 passing in its course behind the foramen ovale. Over its inner 

 two-thirds it bounds the foramen lacerum medium anteriorly, and 

 over its outer third, where it becomes serrated, it articulates with 

 the petrous portion of the temporal, the two forming a groove for 

 the cartilaginous part of the Eustachian tube. The external border 

 separates the superior or cerebral from the external or temporo- 

 zygomatic surface. It is serrated behind, where it is bevelled at the 

 expense of the upper or inner plate, but in front it is squamous and 

 bevelled at the expense of the outer plate. The entire border 

 articulates with the squamous portion of the temporal. The 

 anterior border or malar crest separates the orbital and temporal 

 surfaces. Its direction is downwards and inwards, and it is sharp 

 and irregular for the malar. The internal border is situated between 

 the orbital and cerebral surfaces. Its direction is backwards and 

 inwards, and it forms the lower boundary of the sphenoidal fissure. 

 About its centre it presents a small spine, which gives origin to 

 fibres of the lower head of the external rectus muscle of the eye- 

 ball. The great wing antero-superiorly becomes thick and expanded, 

 and it here presents a rough, triangular, serrated surface for the 

 frontal. At the outer end of this surface there is another small 



