Special Somatic Afferent System 39 



the bundles is a large amount of grey matter, constituting the 

 dorsal nucleus of the lateral lemniscus {nucleus dorsalis lemnisci 

 lateralis). Behind this point its fibres are not very easily 

 distinguished from those of the ventral spino-cerebellar tract 

 (p. 52), which have a similar arrangement and general direc- 

 tion, and which lie immediately lateral and dorsal to the 

 lemniscus. 



The vestibular nerve, which conveys proprioceptive im- 

 pulses, chiefly of an equilibratory nature, ends in relation with 

 a somewhat extensive group of nuclei placed dorso-laterally. 

 These consist of a more or less continuous column of gray 

 matter which is rather clearly divisible into parts. At the 

 level of entry of the root is a large-celled mass in a lateral 

 position close to the ventricle, the lateral vestibular nucleus^ 

 {nucleus lateralis nervi vestibuli) or nucleus ofDeiters (Pis. IX. 

 X.). Extending posteriorly from this, just as the spinal \^ 

 nucleus extends posteriorly from the chief sensory \ nucleus, 

 is the descending vestibular nucleus {nucleus descendens nervi 

 vestibuli seu octavi), which is accompanied by bundles of the 

 root fibres, the descending vestibtdar root (PI. MIL), This 

 root can be traced down as far as the beginning of the spinal 

 cord, where it ends in connection with a small nucleus lying 

 between the cuneate nucleus and the gelatinous substance. 



There are also ascending branches of the root fibres 

 forming an ascending root, as in the case of nerve \, each 

 fibre bifurcating on entering the brain. Many of these 

 ascending branches end in an anterior nucleus, the nucleus of 

 Bechterew or superior vestibular nucleus, which extends from 

 the nucleus of Deiters antero-dorsally, projecting into the 

 cerebellar peduncles (PI. X.). 



Medial to the nucleus of Deiters and the descending 



^Fuse distinguishes seven parts in this nucleus in the rat and other 

 rodents: dorso-lateral, dorsal, middle or central, dorso-medial, ventro- 

 medial, intravestibular, and triangularis portions. He also finds two or 

 three cell groups in the nucleus of Bechterew. 



