

COMPOSITION AND CENTRAL CONNECTIONS OF CRANIAL NERVES 861 



vestibulospinal fasciculus are intimately concerned with equilibratory reflexes. 

 Other axons from Deiters's nucleus are supposed to cross and ascend in the opposite 

 medial lemniscus to the ventro-lateral nuclei of the thalamus ; still other fibers pass 

 into the cerebellum with the inferior peduncle and are distributed to the cortex of 

 the vermis and the roof nuclei of the cerebellum; according to Cajal they merely 

 pass through the nucleus fastigii on, their way to the cortex of the vermis and the 

 hemisphere. 



The superior vestibular nucleus (Bechterew's nucleus*) is the dorso-lateral part of 

 the vestibular nucleus and receives collaterals and terminals from the ascending 

 branches of the vestibular nerve. Its axons terminate in much the same manner 

 as do those from the lateral nucleus. 



! The Facial Nerve (VII cranial) consists of somatic sensory, sympathetic afferent, 

 taste, somatic motor and sympathetic efferent fibers. The afferent or sensory 

 fibers arise from cells in the geniculate ganglion. This portion of the nerve is often 

 described as the nervus intermedius. 



(1) The somatic sensory fibers are few in number and convey sensory impulses 

 from the middle ear region. Their existence has not been fully confirmed. Their 

 central termination is likewise uncertain, it is possible that they join the spinal 

 tract of the trigeminal as do the somatic sensory fibers of the vagus and glosso- 

 pharyngeal. 



(2) The sympathetic afferent fibers are likewise few in number and of unknown 

 termination. 



(3) Taste fibers convey impulses from the anterior two-thirds of the tongue via 

 the chorda tympani. They are supposed to join the tractus solitarius and termi- 

 nate in its nucleus. The central connections of this nucleus have already been 

 considered. 



(4) Somatic motor fibers, supplying the muscles derived from the hyoid arch, 

 arise from the large multipolar cells of the nucleus of the facial nerve. This nucleus 

 is serially homologous with the nucleus ambiguus and lateral part of the anterior 

 column of the spinal cord. Voluntary impulses from the cerebral cortex are con- 

 veyed by terminals and collaterals of the pyramidal tract of the opposite side, 

 indirectly, that is with the interpolation of a connecting neuron, to the facial 

 nucleus. This nucleus undoubtedly receives many reflex fibers from various 

 sources, i. e., from the superior colliculus via the ventral longitudinal bundle 

 (tectospinal fasciculus) for optic reflexes; from the inferior colliculus via the auditory 

 reflex path; and indirectly from the terminal sensory nuclei of the brain-stem. 

 Through the posterior longitudinal bundle it is intimately connected with other 



otor nuclei of the brain-stem. 



(5) Sympathetic efferent fibers (preganglionic fibers) arise according to some 

 .uthors from the small cells of the facial nucleus, or according to others from a 



special nucleus of cells scattered in the reticular formation, dorso-medial to the 

 facial nucleus. This is sometimes called the superior salivatory nucleus. These 

 preganglionic fibers are distributed partly via the chorda tympani and lingual nerves 

 to the submaxillary ganglion, thence by postganglionic (vasodilator) fibers to the 

 submaxillary and sublingual glands. Some of the preganglionic fibers pass to the 

 sphenopalatine ganglion via the great superficial petrosal nerve. 



The Abducens Nerve (VI cranial) contains somatic motor fibers only which 

 supply the lateral rectus muscle of the eye. The fibers arise from the nucleus of 

 the abducens nerve and pass ventrally through the formatio reticularis of the pons 

 to emerge in the transverse groove between the caudal edge of the pons and the 

 pyramid. The nucleus is serially homologous with the nuclei of the trochlear and 

 oculomotor above and with the hypoglossal and medial part of the anterior column 

 of the spinal cord below. It is situated close to the floor of the fourth ventricle, 

 just above the level of the striae medullares. Voluntary impulses from the cerebral 





