222 



THE CRANIAL NERVES. 



pairs. The two arrangements, as well as the special designations of the several nerves, are 

 shown in the following table : 



OTHER NAMES. 



Olfactory nerves. 



Optic. 



Common oculomotor. 



Pathetic or trochlear. 



Trifacial or trigeminal. 



Abducent ocular. 



Facial motor. 



Auditory. 



Grlosso-pharyngeal. 



Pneumo-gastric or vagus. 



Spinal accessory, 



Hypoglcssal or lingual motor. 



Suboccipital. 



Connection with the cerebro-spinal axis. The place at which a cranial 

 nerve is attached to the surface of the cerebro-spinal axis is usually termed the 



Fig. 140. VENTRAL ASPECT OF THE 



BRAIN-STEM, SHOWING THE ATTACH- 

 MENTS OF THE PRINCIPAL CRANIAL 



NERVES. (Allen Thomson.) 



The full description of this figure will 

 be found at p. 41. The following refer- 

 ences apply to the roots of the nerves: 

 I', right olfactory tract, divided near its; 

 middle ; II, left optic nerve, springing 

 from the commissure, which is concealed 

 by the pituitary body ; II', right optic 

 tract ; the left tract is seen passing back 

 into i arid e, the internal and external 

 corpora geniculata; III, left oculomotor 

 nerve ; IV, trochlear : V, V, large roots 

 of the trifacial nerves ; + + , small 

 roots, the + of the right side is placed 

 on the Gasserian ganglion ; 1, ophthal- 

 mic, 2, superior maxillary, and 3, in- 

 ferior maxillary nerves ; VI, left abducent 

 nerve ; VII, facial ; VIII, auditory ; IX, 

 glosso-pharyngeal ; X, pneumo-gastric ; 

 XI, spinal accessory ; XII, right hypo- 

 glossal nerve ; at o, on the left side, the 

 rootlets are seen cut short ; C I, sub- 

 occipital or first cervical nerve. 



superficial origin of the nerve. 

 From this apparent origin the 

 nerve-roots can be traced for a 

 variable depth within the sub-^ 

 stance of the axis to certain col- 

 lections of nerve-cells or nuclei, 

 the connection with which is said 

 to constitute the deep origin of 

 the nerve. It is evident, how- 

 ever, that these terms are pro- 

 perly applicable only to the central connections of the motor or efferent nerves, 

 the fibres of which are outgrowths of nerve-cells contained in the respective nuclei, 

 whereas the sensory or afferent fibres originate generally in the cells of the ganglia 

 found upon the nerve-trunks in the immediate neighbourhood of the axis, and grow 



