ORIGIN OF THE "CRANIAL NERVES. 



83 



CONNECTIONS OF THE CRANIAL NERVES WITH THE ENCEPHALON. 



The roots of the cranial nerves may be traced for some depth into the 

 substance of the encephalon, a circumstance which has led to the distinction 

 of the deep or real origin, and the superficial or apparent origin, by which 

 latter is understood the place at which the nerve appears to be attached to 

 the surface of the encephalon. The superficial origin of these nerves is 

 quite obvious, but their deeper connection is, in most cases, still a matter 

 of some uncertainty. 



Fig. 397. VIEW FROM 



BELOW OF THE CONNEC- 

 TION OF THE PRINCIPAL 

 NERVES WITH THE 

 BRAIN. 



The full description of 

 this figure will be found 

 at p. 538. The following 

 references apply to the 

 roots of the nerves : I', 

 the right olfactory tract 

 divided near its middle ; 

 II, the left optic nerve 

 springing from the com- 

 missure which is con- 

 cealed by the pituitary 

 body ; II', the right optic 

 tract; the left tract is 

 seen passing back into 

 i and e, the internal and 

 external corpora genicu- 

 lata ; III, the left oculo- 

 motor nerve ; IV, the 

 trochlear ; V, V, the 

 large roots of the tri- 

 facial nerves ; + + , the 

 lesser roots, the -r of the 

 right side is placed on 

 the Grasserian ganglion ; 

 1, the ophthalmic ; 2, the 

 superior maxillary, and 

 3, the inferior maxillary 

 nerves ; VI, the left ab- 

 ducent nerve ; VII, a, &, 

 the facial and auditory 

 nerves ; a, VIII, 6, the 

 glosso-pharyngeal, pneu- 

 mo -gastric, and spinal ac- 

 cessory nerves ; IX, the 

 right hypoglossal nerve ; 

 at o, on the left side, the 

 rootlets are seen cut- 

 short ; C I, the left sub- 

 occipital or first cervical 

 nerve. 



Fig. 397. 



Ci 



cL ca 



1. The first or olfactory nerve, as it is usually described, small in man in 

 comparison with animals, lies on the under surface of the anterior lobe of the 

 cerebrum to the outer side of the longitudinal median fissure, lodged in a 

 sulcus between two straight convolutions. Unlike other nerves, it consists 

 of a large proportion of grey matter mixed with white fibres, and indeed 



