764 DR ALEXANDER BRUCE AND DR JAMES W. DAWSON ON 
a reticulum. An area of the posterior columns, with nucleated fibres mostly cut 
transversely, is situated almost invariably just to the inner side of the fibrosed 
root-entry zone. 
In longitudinal sections of the cord, the entering posterior root fibres can be 
traced for fully one centimetre: the fibres show neurilemma sheath and nucleus 
and an increased interfibrillar tissue. The nuclei in relation to the fibres tend to 
assume a position actually within the contour of the nerve fibre, and the nucleated 
fibres end in direct continuity with normal non-nucleated fibres of the posterior 
columns. No definite fusiform elements could be traced in relation to the termina- 
tions of these nucleated fibres. 
Weigert-fuchsin preparations show that very many of the fibres in the posterior 
root-entry zone and in the areas mesial to it are degenerated; in some nerve fibres 
only a faint shadow of myelin is present. That this again was not due to over- 
differentiation was proved by the presence of the very fine fibres in the pia immediately 
anterior to the posterior roots. Under low power, the posterior root-entry zone stood 
out clearly as an area of diffuse fibrosis, continuous with an oval area immediately 
internal to it, which was probably the continuation upwards of the root-entry zone 
of lower levels. 
The 5th cervical seoment showed only a slight trace of this fibrosis in the 
posterior root-entry zone, but in the area internal to it were numerous nucleated 
fibres, each with a delicate pink zone. In these nucleated patches the normally 
situated glia cells were very much enlarged, and the thickened, ramifying processes 
formed a fine network around the fibres, the nuclei of which could be distinguished 
from glia nuclei by their intimate relation to the axis-cylinder. 
It is important to note that though so many of the fibres in the intra-medullary 
portion of the posterior roots showed degeneration, there was no attempt at a 
regeneration from the healthy extra-medullary portion. None of the fibres in the 
lateral pia could be traced directly to posterior roots, nor could any definite connection 
be established between posterior roots and the few pial fibres in the posterior pia 
and pial septa. NacGrorre, as we have seen, has described in tabes a collateral 
regeneration from the preserved end of the posterior roots, and Raymonp traced 
the fibres of the neuromata, found by him in the posterior pia, to a regeneration of 
posterior root fibres interrupted in their intra-medullary course. An explanation 
of this absence of regeneration may be found in the integrity of the axis-cylinder 
as revealed by the silver method. 
(4) SciERosIs. 
Areas of sclerosis are here distinguished from areas of fibrosis, though the latter 
frequently extended so as to involve the former. We may here confine ourselves 
to a reference to those areas in which no marked fibrosis accounted for the change, 
