448 MESSRS. F. GOTGH AND V. HORSLEY 



their peripheral side, or issue in such broken and disorderly array that their 

 character is completely lost, and all evidence of their presence disappears. 



To what extent is this true of the afferent root fibres ? The answer to this question 

 is one which can only be appreciated when the results of the experiments of both this 

 chapter and the succeeding one, upon the reflex functions of the cord, have been 

 analysed ; but it may be well here to state at once that there is no evidence of such 

 pronounced block to impulses which may be caused to descend the indirect paths by 

 which the posterior root fibres are brought into connection with the cord. 



The difficulties of interpreting the experimental results are increased by the gap 

 which exists in our anatomical knowledge as to the connection between these indirect 

 afferent fibres and the cord. This connection is one upon which the degeneration 

 method throws but little light, although it would appear probable from the trophic 

 changes observed, and from morphological considerations, that there are cells in the 

 posterior horn, and possibly in CLARKE S column, which are connected with fibres 

 in the posterior roots (MoT f). The recent researches of KOLLIKER seem to indicate 

 that the termination of some of these indirect fibres in the cord is largely that of 

 a fine plexus with free ends. 



Although the central connections of the fibres are as yet to a great extent 

 unknown, yet the description indirect as distinguished from direct is warranted by 

 its wide-spread use. It is advisable, however, to emphasise what the term indirect 

 as used by us in the present case is understood to connote. 



It is descriptive of all afferent fibres in, the cord, which may be supposed to be 

 connected with those of the posterior root, but which do not show any of the 

 degenerative and developmental differences which stamp some fibres (posterior 

 median) as being in direct continuity with the root. There is, however, nothing in 

 itself to show that this term indirect is a strictly logical one ; since the same line 

 of argument might be applied to those fibres which pass through the ganglion on the 

 posterior root, with regard to which the degeneration method furnishes no evidence 

 of direct continuity (JOSEPH). 



Impulses are conducted through the ganglion in either direction (DU Bois- 

 EEYMOND), and apparently without any modification in their time relations (EXNER) 

 if we may suppose that this is due to the fact that, apart from the few fibres which 

 appear not to come into relation with cells at all, the relationship of the majority of 

 fibres to the ganglion cells is of the ~J~-piece kind, as shown by RANVIER, in which 

 case the cell does not interrupt the continuity of the connected fibre. There is no 

 reason why some such sort of bypath (GoLGi) may not be the basis of the con 

 nection of the fibres with the corpuscular elements in the spinal cord, as it is in 

 certain parts of the cerebrum (FLECHSIG). 



There are, therefore, no anatomical data which are necessarily implied in the term 

 indirect as applied to these fibres, beyond the fact that such fibres come into 



