CHAPTEK XI. 



y 

 THE CRANIAL NERVES AND ORGANS OF SENSE. 



GENERAL CONSIDERATIONS CLASSIFICATION OF THE CRANIAL NERVES TABLE OF THE 

 CRANIAL NERVES SKIN TONGUE NOSE EYE AND ITS APPENDAGES EAR. 



1372. The Cranial Nerves General Considerations. As 

 briefly described in 996, 1007, and shown in Fig. 104, 109, most 

 of the nerves of the trunk and limbs are connected with the myelon 

 by two sets of roots which respectively emerge from its dorso-lateral 

 and ventro-lateral aspects opposite the dorsal and ventral cornua of 

 the cinerea. The dorsal roots bear each a ganglion, and they are 

 sensory, while the ventral have no ganglion (Fig. 109) and are 

 motor. 



Each dorsal root is joined by a corresponding ventral root, and 

 the trunk so formed has both motor and sensory functions. 



The roots and trunks vary in size and in the number of their 

 rootlets and branches ; they vary also to some extent in their rela- 

 tions with the sympathic nerves and the viscera. Upon the whole, 

 however, they form a series all the members of which are readily 

 and quite closely comparable. 



1373. But the cranial nerves (which either arise from the 

 encephalon or eventually escape through cranial foramina) present 

 no such simplicity in any animals, and in man and most mammals 

 their irregularities in origin and distribution are so great that the 

 older anatomists seem not to have attempted any comparison with 

 the myelonal type. Their functions likewise were imperfectly 

 known, and they were therefore numbered in order, beginning at 

 the cephalic end of the brain, and their names referred mainly to 

 their anatomical connections. 



