OCULO-MOTOE NEEVE. 



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terminates in connection with the pulvinar, the lateral geniculate body the superior 

 brachium, and the medial geniculate body all of the same side. 



When the optic nerve reaches the optic chiasma some of its fibres pass to the optic 

 tract of the same side and some to the optic tract of the opposite side. Therefore, 

 each optic nerve is connected with both sides of the brain. But each optic tract, in 

 addition to some fibres of both optic nerves, contains also fibres passing from the 

 medial geniculate body of one side to the medial geniculate body of the opposite side. 



FIG. 644. CENTRAL CONNEXIONS OF THE OPTIC NERVE AND OPTIC TRACTS. 



In the orbital portion of its course the optic nerve is surrounded by sheaths of 

 the membranes of the brain, and by a sheath of fascia bulbi, as well as by the fat and 

 muscles ; and it is crossed by the ophthalmic artery and the naso-ciliary nerve. It 

 3 pierced on its inferior surface by the central artery of the retina, and as it 

 approaches the eyeball it is surrounded by the ciliary vessels and nerves. 





NERVUS OCULOMOTORIUS. 



The third or oculo-motor nerve arises from the brain, in the region of the 



terior perforated substance, by several fila radicularia (radicles) emerging from 



i oculo-motor sulcus, on the medial side of the cerebral peduncle, just in front 



of the pons (Fig. 643). Passing forwards between the posterior cerebral and 



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