_b._ The second, or optic, passes out by a large hole, the =optic foramen= (fig. 75, II) piercing the orbitosphenoid. The optic foramen is the most anterior of the three prominent holes seen within and immediately behind the orbit. _c._ The third, fourth, and sixth nerves, i.e. those supplying the eye muscles, and with them the first or ophthalmic branch of the large fifth or trigeminal nerve, pass out by a large hole, the =foramen lacerum anterius= (fig. 75, III, IV, V{1}, VI), which, as has been already mentioned, lies between the orbitosphenoid and alisphenoid. _d._ Immediately behind the foramen lacerum anterius, the alisphenoid is perforated by a prominent round hole, the =foramen rotundum= (fig. 75, V{2}), through which the second branch of the trigeminal nerve passes out. _e._ A quarter of an inch further back there is another prominent hole, the =foramen ovale= (fig. 75, V{3}), through which the third branch of the trigeminal nerve leaves the cranium. _f._ The seventh or facial nerve, as already mentioned, leaves the cranial cavity and enters the auditory capsule, through an opening in the periotic called the =internal auditory meatus=, while it finally leaves the skull by the =stylomastoid foramen= (fig. 75, VII), which lies between the tympanic bulla, the paroccipital process, and the mastoid portion of the periotic. _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.