900 



THE NERVOUS SYSTEM 



(d) The nuclei receive fibres from the grey substance of the vermis. It is probable 

 that all the nuclei of termination give off fibres bearing ascending impulses which 

 ultimately reach the somtesthetic area, but the course pursued and neurones 

 involved in such a chain are uncertain. 



VII. The Attditory Conduction Path (Cochlear Nerve) 



1. Spiral ganghon of the cochlea gives origin to short peripheral fibres to organ of 



Corti, and to the centrally directed cochlear nerve. 



2. Dorsal and ventral nuclei of the cochlear nerve (nuclei of termination). 



(a) Striae medullares arise from dorsal nucleus and pass around outer side of resti- 

 form body (acoustic tubercle), then medianward under ependyma of floor 

 of fourth ventricle to mid-line, then ventralward into tegmentum, where 

 they decussate and join trapezoid body and lateral lemniscus of opposite side. 



Fig. 708. — Diagram Showing Some of the Connections op the Vestibular and Cochleae 



Nerves. 



Inferior quadrigeminate body 



Nucleus of trochlear nerve 



Nucleus fastigii 



Nucleus emboliformis 



Nucleus of lateral lemniscus 



Medial longitudinal fasciculus 



Lateral lemniscus 



Peduncle of superior olive 



" Dentate nucleus 



^ Lateral nucleus of 

 " ' vestibular nerve 

 .^Restiform body 

 Dorsal nucleus of 

 cochlear nerve 

 ^^ Ventral nucleus of 



cochlear nerve 

 , •Cochlear nerve 



Vestibular nerve 

 Superior olivary nucleus 



Trapezoid body 



(fc) 



Fibres arising in ventral nucleus pass ventrally medianward and some termi- 

 nate in the superior olivary nucleus of same side; others pass by way of trapezoid 

 body and lateral lemniscus to terminate in superior olivary nucleus, nucleus 

 of lateral lemniscus, medial geniculate body and nucleus of inferior quadri- 

 geminate body of the opposite side. 

 Nuclei of superior oUves of both sides and nucleus of lateral lemniscus send fibres 

 by way of lateral lenmiscus to inferior quadrigeminate body and through inferior 

 brachium to medial geniculate body, and some may pass uninterrupted to the 

 cortex of the temporal lobe. 



Fibres from medial geniculate body and probably from nucleus of inferior quadri- 

 geminate body pass into internal capsule and through temporal part of corona radiata 

 to middle third of superior temporal gyrus and adjacent portions (auditory area). 

 From .striaj medullares and from superior olivary nucleus (peduncle of superior olive) 

 arise fibres which terminate in nucleus of abducens or pass by way of the medial 

 longitudinal fasciculus to other motor nuclei of cranial nerves. It is probable that 

 fibres from the auditory area of the cerebral cortex are also distributed to nuclei of 

 the cranial nerves. 



VIII. Conduction Paths of the Optic Apparatus 

 A . Optic impulses. 



1. 'Bipolar' cells of retina with short (peripheral) processes to layer of rods and cones 

 (neuro-epithclium) and short centrally directed processes to ganghon-cell layer 

 of retina (nucleus of termination). 



5. 



