THE NERVE FIBRE 



113 



FlG. 111. GoLGI CELL, TYPE II. 



a, neuraxis, which immediately 

 breaks into a network of fine col- 

 laterals. Golgi's stain. (After 

 Andriezen, from Obersteiner.) 



The parent stem of the neuraxis may be finally exhausted in its 

 collaterals, or it may in turn end in a terminal arborization. Col- 

 laterals are said to be more frequent in the proximal than in the 

 distal portion of the neuraxis. 



According to the length of their 

 neuraxis, neurones were divided by 

 Golgi into two types : 



1. Golgi cells, Type I (Deiter's 

 cells). 



2. Golgi cells, Type II (Golgi's 

 cells). 



The cells of Type I possess a long 

 neuraxis which passes beyond the con- 

 fines of the grey matter in which it 

 arises and usually becomes the axis 

 cylinder of a nerve fibre. 



The cells of Type II possess a short 

 neuraxis which forms its terminal ar- 

 borization in the vicinity of its parent 

 cell body. The cells of this type are 

 usually association neurones; they place in conduction relation 

 other not very remote neurones. The cells of Type I, on the 

 other hand, are more frequently projection neurones; they are 

 distributed from the nerve centers to other and perhaps very 

 different tissues, their course lying in the long projection tracts 

 and nerve trunks of the nervous system. 



The cells of Type II are therefore most frequently intrinsic 

 or endogenous neurones, their whole course lying in one division 

 of the central nervous system, e. g., the grey matter of the spinal 

 cord. The cells of Type I are more frequently extrinsic or exoge- 

 nous ; they arise in one part of the nervous system to be distributed 

 to a distant portion, e. g., they arise in the peripheral ganglia and 

 enter the spinal cord to terminate in its grey matter, or vice versa. 



THE NERVE FIBRE. The origin of the nerve fibre and its 

 relation to the other portions of the neurone will be appreciated 

 by tracing the course of the neuraxis of a motor nerve cell of the 

 ventral horn of grey matter in the spinal cord. This process, ari- 

 sing in the central grey matter, is at first a naked neuraxis. It 

 soon leaves the grey matter to traverse the white matter and 

 makes its exit from the spinal cord as the axis cylinder of one of 

 the fibres of an anterior nerve root. On leaving the grey matter 



