960 NUCLEI OF CRANIAL NERVES. [BOOK in. 



When we trace the ventral root, vestibular nerve (Fig. Ill), 

 inwards we find that making, according to most observers, no 

 connections at all with the accessory nucleus, it passes (Fig. Ill, 

 viii.) to the median side of the restiform body, between it and 

 the ascending root of the fifth nerve, and so reaches the lateral 

 division of the nucleus, in the large cells of which most at least 

 of its fibres are said to end and which therefore may be regarded 

 as the nucleus of the ventral root. On this point however all 

 authors are not agreed. The lateral auditory nucleus, with the 

 fibres proceeding to and from it, lying as they do to the median 

 or inner side of the restiform body proper, are sometimes spoken 

 of as the median or inner division of the restiform body; and 

 from the nucleus a considerable number of fibres pass up with 

 the restiform body into the cerebellum as a continuation of this 

 " median division of the restiform body." Some authors maintain 

 that these fibres are continued straight on from the nerve to the 

 cerebellum ; but the more recent investigations seem to shew that 

 they all make connections with the nerve cells of the lateral nucleus 

 on their way. These fibres constitute a connection between the 

 auditory (vestibular) nerve and the cerebellum, the physiological 

 significance of which we shall see later on ; we may perhaps 

 compare it to the connection between the posterior roots of the 

 spinal nerves and the cerebellum through (the vesicular cylinder 

 and) the cerebellar tract. 



The other central connections of the lateral nucleus are, like 

 those of the accessory and of the median nucleus, complicated and 

 obscure. But we may call attention to a set of fibres which, 

 starting apparently in the accessory nucleus, run directly trans- 

 verse in the ventral region of the tegmentum just dorsal to the 

 transverse fibres of the pons, forming what is called the trapezium 

 (Fig. Ill, Tp.). 



Lastly, we may add that the fibres of the peculiar portio 

 intermedia appear to take origin from the accessory nucleus. 



619. The Seventh or Facial Nerve. The nucleus (Fig. 115, 

 VII. and Figs. 110, 111, VII. ??.), of this nerve (it being 

 borne in mind that the motor fibres for the orbital region (the 

 orbicular muscle &c.), though they run in the trunk of this nerve, 

 really belong to the third nerve and take origin from the hind 

 part of the nucleus of the third nerve) narrower in front than 

 behind, reaches from the level of the striae acusticae some 

 distance into the region of the pons, and occupies in the midst 

 of the reticular formation, a little dorsal of the patch of grey 

 matter called the upper olive, a position corresponding closely to 

 that of the nucleus ambiguus. The cells of the nucleus are large, 

 and possess well-marked axis-cylinder processes, which are gathered 

 up at the dorsal surface of the nucleus to form the root. This, 

 rising up dorsally, describes a loop (Fig. Ill, VII. g.) round the 

 nucleus of the sixth or abducens nerve, running forward for some 



