324 EGBERT J. TERRY 



within the cave : the ganglion semilunare and the three divisions 

 of the N. v., the NN. Ill, IV and VI. The caudal half of the 

 semilunar ganglion rests upon the supracochlear plane, in its 

 cephalic half upon the alicochlear commissure and the posterior 

 subdivision of the dorsal surface of the lamina ascendelis. Be- 

 neath it, the mandibular nerve passes to leave the cave through 

 the incisura ovalis. The ophthalmic and maxillary nerves leave 

 the region immediately in front of the ganghon, the one by way 

 of the spheno-orbital fissure, the other by the foramen rotundum. 

 Both the oculomotor and trochlear nerves run a long course in 

 the loose tissue immediately surrounding the brain, proceeding 

 from their origins ventrad and cephalad toward the spheno- 

 orbital fissure, where they lie above the ophthalmic nerve. They 

 pierce the membrana Imiitans just before entering the fissure, 

 and their course in the epipteric cave is therefore very short 

 (fig. 23). On the contrary, the course of the abducent nerve 

 through the cavum epiptericum is very long ; it enters the space 

 from behind, passing between the dorsum sellae and cochlear 

 capsule, over the crista transversa and beneath that strand of 

 condensed mesenchyma in the septum transversum which is the 

 forerunner of the cartilage referred to above. Running cephalo- 

 laterad, it crosses laterally the carotid artery and gains the medial 

 side of the semilunar ganghon and ophthalmic nerve; in the spheno- 

 orbital fissure it crosses dorsally the N. maxillaris. The internal 

 carotid artery enters the membrana limitans at the carotid fora- 

 men, turns forward in this tissue, crosses the processus alaris at 

 the side of the hypophysis, then pierces the membrane in a dor- 

 sal and medial direction to enter the cavum cranii. At its en- 

 trance into the basal portion of the membrana hmitans the artery 

 is ventrad of the sixth nerve, but it turns immediately mesad 

 beneath it. Several veins accompany the nerves through the 

 spheno-orbital fissure and go to form, by anastomoses, a plexus 

 in the membrana limitans which surrounds the carotid artery. 

 The vessels of this plexus are separated by mesenchymal tissue, 

 altogether constituting the beginnings of the channels and walls 

 of the later cavernous sinus. 



