Atlas and text-book of topographic and applied anatomy . vein, the larger of the two,is situated at first at the inner side of the orbit; it passes outward between the optic nerve and thesuperior rectus and empties into the cavernous sinus through the sphenoidal fissure. At theinner canthus this vessel anastomoses with the angular vein (from the facial) and with the frontalvein (see Plate 2). The injerior ophthalmic vein arises in the central portion of the floor of theorbit and empties partly through the sphenoidal fissure into the cavernous sinus and partlythrough the spheno-maxillary fissur
Atlas and text-book of topographic and applied anatomy . vein, the larger of the two,is situated at first at the inner side of the orbit; it passes outward between the optic nerve and thesuperior rectus and empties into the cavernous sinus through the sphenoidal fissure. At theinner canthus this vessel anastomoses with the angular vein (from the facial) and with the frontalvein (see Plate 2). The injerior ophthalmic vein arises in the central portion of the floor of theorbit and empties partly through the sphenoidal fissure into the cavernous sinus and partlythrough the spheno-maxillary fissure into the region drained by the facial vein. This inferiorophthalmic vein may be absent. Valves are not present in any of these veins. The nerves oj the orbit, in addition to the optic, are the sensory first division of the trifacial, THE ORBITAL CAVITY. 47 the ophthalmic, with its three branches, and the nerves supplying the ocular muscles—the oculo-motor, the trochlear, and the abducent. All these nerves, except the optic, enter the orbit through. Occipital bone Fig. 17.—A horizontal section of the head in the plane of the palpebral fissures (frozen section). The plane ofsection passes through the orbits in such a way as to show the entire length of the optic nerves as well as a portion ofthe optic chiasm. The cerebellum lies in the posterior cerebral fossa and is covered in by the tentorium cerebelli, whichhas been left intact. In the incisura tentorii may be seen the cross-sections of the two cerebral peduncles; the entirecerebrum has been removed. 48 TOPOGRAPHIC AND APPLIED ANATOMY. the sphenoidal fissure. The most superficial nerve, and the one first exposed beneath the perior-bita after chiseling open the orbit from the frontal cavity, is the frontal branch (upon the levatorpalpebrae superioris) of the ophthalmic nerve, which has already been mentioned in the sectionupon the scalp. The second branch of the ophthalmic nerve, the lachrymal (to the lachrymalgland), is
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