153 OUTLINES OE EQUINE ANATOMY. 



^"he centre of tlie cranial surface of the petrous temporal 

 bone. It gives passage to the seventh and eighth nerves, 

 aad runs to the internal ear though it gives off a portion 

 which passes to the middle ear. On the upper surface of the 

 body of the sphenoid, laterally are broad channels through 

 which the superior maxillary division of the fifth runs, and 

 thus gains the foramen rotundum, which, in proceeding to 

 the bottom of the orbit, unites with the sub-spherioidal fora- 

 men, which passes through the wing of os sphenoides, and 

 which gives passage to the internal maxillary artery. Thus 

 through the anterior part of the foramen rotundum, the 

 superior maxillary division of the fifth nerve and the in- 

 ternal maxillary artery pass. Just above this and situated 

 between the ethmoid and the sphenoid bones is foramen 

 lacerum orhitale, through which the third, fourth, ophthalmic 

 division of the fifth and sixth nerves, and the ophthalmic 

 artery and vein run (the ophthalmic vein connects the 

 superior varicose vein of the face with the cavernous sinus). 

 In front of the sella turcica or upper surface of the body 

 of the sphenoid, there are two foramina running forwards 

 through the ethmoid bone connected anteriorly by a space 

 which is covered by the inferior extremity of the cristagalli 

 process and in which the optic decussation rests. These 

 are the foramina optici. They give passage to the optic 

 nerves covered by their dense sheath of dura mater, and 

 open into the lower part of the orbits by a common opening, 

 which they share with the foramina lacera orbitale, and 

 rotunda. This is the sphenoideal hiatus, just above its 

 superior rough margin is forame7ipathetici, which only gives 

 passage to a few small vessels. Internally situated is fora- 

 men orhitale internum, which passes to the outer lateral 

 part of the ethmoidal fossa, thus passing directly into the 

 cranial cavity. Through it the lateral nasal artery and 

 vein run. Numerous other foramina are found passing 

 through the cranial walls, but are unnamed ; through them 

 pass vessels and nerve-fibres. Some others are generally 

 enumerated as cranial foramina, though they do not pass 

 into the cranial cavity. Foramen auditorium externum 

 runs through the external auditory process, and at the 

 middle ear, in the recent subject, presents the membrana 

 tympani. It is lined by common integument. Foramen styloi- 

 deum is that opening through which the facial nerve emerges 

 from the middle ear ; it is divided into two parts ; from 



