g. The eighth or auditory nerve on leaving the cranial cavity, passes with the facial straight into the auditory capsule through the internal auditory meatus (fig. 72, 20). It is then distributed to the organ of hearing.
h. The ninth, tenth and eleventh nerves leave the skull through the foramen lacerum posterius (fig. 75, IX, X, XI), a large space lying between the auditory bones and the exoccipital.
i. Finally, the twelfth nerve, the hypoglossal, passes out through the prominent condylar foramen (fig. 75, XII), which perforates the exoccipital just behind the foramen lacerum posterius.
II. Other Openings in the Skull.
a. The anterior narial opening lies at the anterior end of the skull, and is bounded by the premaxillae and nasals. In the natural condition it is divided into two by a vertical partition, formed by the narial septum, the anterior unossified part of the mesethmoid.
b. Penetrating the middle of the maxillae at the side of the face is the rather large infra-orbital foramen (fig. 73, 11), through which part of the second branch of the trigeminal nerve passes out from the orbit to the side of the face.
c. Several foramina are seen perforating the anterior part of the orbit. The most dorsal of these, perforating the lachrymal bone, is the lachrymal foramen (fig. 73, 13). Lying below and slightly external to this is a large foramen, through which part of the second branch of the trigeminal enters on its way to the infra-orbital foramen and so to the side of the face. Lastly, lying below these, and perforating the palatine, are two closely apposed foramina, the internal orbital foramina, through which part of the first or ophthalmic branch of the trigeminal nerve leaves the orbit, passing into the nasal cavity.
d. The anterior part of the palate between the premaxillae and the maxillae is perforated by a pair of long closely apposed apertures, the anterior palatine foramina (fig. 75, 19). They transmit part of the trigeminal nerve.
e. Towards the posterior part of the palate are two pairs of small posterior palatine foramina (fig. 75, 18). These perforate the palatine and transmit branches of the trigeminal nerve and certain blood-vessels.
f. The posterior narial opening is bounded chiefly by the palatines.