ix. I OF THE DOG. i 



3. At a very short distance behind this is a more irregular^ 

 oval opening, between the orbitosphenoid and the ali- 

 sphenoid. This is the sphenoidal or orbital fissure, or( 

 foranwi lacerum antcriuj. It leads * into the orbit, and 

 allows the exit of the motor nerves of the eyeball, or third, 

 fourth, and sixth cranial nerves, and also the third division 

 f the trigeminal or fifth nerve. 

 4 and 5. The alisphenoid near its base is perforated by 

 o foramina ; the anterior small and somewhat round ; the 

 sterior larger and oval : these are the foramen rotundum 

 d the forameii ovale, and transmit respectively the second 

 d third divisions of the fifth nerve. 



6. Between the alisphenoid and the exoccipital is a large 

 ace, almost entirely filled by the bony capsule of the organ 



hearing, the periotic. In front of the inner end of this 

 ne is an opening {foramen lacerum medium basis cranii), 

 rough which the internal carotid artery sometimes enters 

 e cranial cavity. 



7. Near the middle of the inner surface of the periotic ( 

 the meatus auditorius interims, into which the seventh ! 

 d eighth nerves enter : the former (the facial nerve) 

 sses through the bone and emerges on the other side 



(by the stylo-mastoid foramen) ; the latter, the auditory, is 

 distributed to the internal organ of hearing within the / 

 periotic bone. 



A deep depression seen above the internal auditory 

 meatus, and of nearly the same size, is not a foramen but a 

 fossa, lying within the concavity of the superior semicircular 

 canal. It lodges the flocculus, a small process of the cere- 

 bellum. 



8. Between the periotic and the exoccipital an irregular^ 

 space is left (the foramem lacerum posterius), through which j 

 the glossopharyngeal, pneumogastric, and spinal accessoryS 



