50 OSTEOLOGY, OR ANATOMY OF OSSEOUS SYSTEM 



nerve. Behind and external to this is the foramen ovale, near 

 the posterior margin of the great wing, sometimes incomplete; 

 it transmits the inferior maxillary nerve, the small meningeal 

 artery, and sometimes the small superficial petrosal nerve. 

 The foramen spinosum pierces the great wing near the posterior 

 angle, and transmits the middle meningeal artery and nervus 

 spinosus, a recurrent branch of the inframaxillary. From 

 the foramen spinosum projects backward a thin horizontal 

 spheno petrosal lamina, which reaches the upper border of the 

 Eustachian canal on the petrous. 



The Vidian canal pierces the base of the internal pterygoid 

 plate anteroposteriorly ; it passes from the foramen lacerum to 

 the sphenomaxillary fossa, transmitting the Vidian nerve and 

 vessels. 



A spicule of bone may connect the middle clinoid process 

 (when present) with the anterior, forming a caroticoclinoid 

 foramen for the carotid artery. Interclinoid ligaments are 

 normally present beneath the dura. The outer pterygoid 

 plate may be connected by bone or ligament with the spinous 

 process. The foramen of Vesalius for an emissary vein is some- 

 times present on the inner side of the foramen ovale. The 

 canaliculus innominatus is sometimes present for the small 

 superficial petrosal nerve internal to the foramen spinosum. 



The Ethmoid Bone 



The ethmoid (sieve-like) projects down between the orbital 

 plates of the frontal, and enters into the formation of the 

 cranium, orbits, and nasal fossae. 



It articulates with thirteen bones fifteen including the 

 sphenoidal turbinates the frontal, sphenoid, and vomer, 

 the nasals, lacrymals, superior maxilla?, palatals, and inferior 

 turbinate bones. 



It consists of thin plates enclosing irregular cells a vertical 

 plate and two lateral masses united above by the horizontal 

 cribriform plate. The vertical plate forms the upper third of 

 the nasal septum, and presents grooves and canals for the 

 olfactory nerves. Its superior border appears in the cranial 

 cavity as the crista (jnlli (cock's comb); posteriorly this process 

 is thin, and anteriorly is broadened into two alar processes, 

 betw r een which is usually a groove completing the foramen 



