THE NERVOUS SYSTEM I34i 



(inner) root of the olfactory tract, and is continuous with the 

 callosal gyrus. 



The optic tract curves round the cms cerebri from without in- 

 wards. The two optic tracts, havong converged, are connected by 

 the optic commissure, which lies at the anterior part of the inter- 

 peduncular space. The optic nerve is connected with the lateral 

 extremity of the front part of the optic commissure. 



The third or oculo-motor nerve emerges through the oculo-motor 

 sulcus on the inner aspect of the cms cerebri, just above or in 

 front of the pons \'arolii, and close to the locus perforatus posticus. 



The fourth, pathetic, or trochlear nerve, ha\Tng emerged from 

 the upper part of the superior medullary velmn, or valve of Vieussens, 

 makes its appearance in the interval between the cms cerebri 

 internally and the temporal lobe externally. 



The fifth, trigeminal, or trifacial nerve consists of two roots, 

 which emerge, close together, from the lateral aspect of the ventral 

 surface of the pons \'arohi. The sensory root is large, and the 

 motor root, which is small, lies above and slightly internal to the 

 sensory root. 



The sixth or abducent nerve emerges at the lower border of 

 the pons Varolii, ]ust external to the pyramid of the medulla 

 Dblongata. 



The seventh or facial nerve {portio dura) emerges at the lower 

 border of the pons, in front of the restiform body of the medulla 

 oblongata. 



The eighth or auditory nerve [portio mollis) hkewise emerges at 

 the lower border of the pons, in front of the restiform body of the 

 medulla oblongata. It lies on the outer side of the facial nerve. 



The pars intermedia of Wrisberg is a small nerve which appears 

 between the facial and auditor\' nerv^es. 



The ninth or glosso-pharyngeal nerve emerges, in the form of 

 about six fasciculi, from the postero-lateral sulcus of the medulla 

 oblongata, between the ohvary body and the restiform body, 

 immediately below the facial ner\-e. 



The tenth or pneumogastric nerve lies directly below the glosso- 

 pharyngeal nerve, and emerges by several fasciciili from the postero- 

 lateral sulcus of the medulla oblongata in front of the restiform 

 body. 



The eleventh or spinal accessory nerve has several roots which 

 he below the fasciculi of the pneumogastric ner\'e. These emerge 

 from the medulla oblongata and the upper part of the lateral 

 column of the spinal cord as low as the level of the fifth cervical 

 nerve, and they lie below the fasciculi of the pnemnogastric ner\'e, 

 and external to, or in front of, the posterior roots of the adjacent 

 cervical spinal nerves. 



The twelfth or hypoglossal nerve emerges by several fasciculi 

 through the antero-lateral sulcus of the medulla oblongata, between 

 the pyramid and the olivary body. These fasciculi Ue in line with 

 the sixth nerve superiorly, 



