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MULTIPLE NEUROMATA OF THE CENTRAL NERVOUS SYSTEM. 763 
vessel represented in fig. 16 can be traced throughout its whole extent from the 
anterior fissure, curving into the grey matter, and passing to the neck of the posterior 
horn. In its course it is surrounded by dense masses of deeply-staining round cells, 
and a small area of calcification was associated with this accumulation. Below the 
5th lumbar segment, the secondary involvement of the strands and nodules was very 
much less marked. 
(3) Frprosis oF THE INTRA-MEDULLARY PoRTIONS OF THE ANTERIOR AND 
PosrERIoR NERVE Roots. 
This change in relation to the anterior nerve roots was constant throughout the 
lumbo-sacral cord, was very irregular in the dorsal cord, and was again present in 
the 7th and 8th cervical segments. In the anterior root-emergent zone the 
divergence peripheralwards of the bundles of fibres was much wider than the normal : 
definite bundles seemed to pass to the antero-mesial angle of the anterior columns and 
even posterior to this angle, and emerging bundles radiated outwards to a point 
considerably more than half way to the ligamentum denticulatum. The whole of this 
root-emergent zone was involved at certain levels in a fibrosis which gave to longi- 
tudinal fibres a deeply-staining pink outline, and to transverse fibres just within the 
pia a sharp pink contour, for each individual fibre was separately enclosed. The 
myelin sheath of such fibres was frequently degenerated as far as the fibrosis extended, 
but silver preparations showed that the axis-cylinders were preserved. This accounts 
for the absence of degeneration in the extra-medullary portion of the anterior roots 
in spite of the degeneration within the cord. Sometimes the whole anterior root- 
emergent zone showed this change; at other times only individual bundles of fibres 
(fig. 54), along each of which it seemed as if the neurilemma, together with a layer 
of the pia, had been continued inwards. The extra-medullary portion of the root did 
not share in this fibrosis. 
The change in the posterior roots was even more striking and constant. Fig. 53, 
taken from the 7th cervical segment, shows that the fibres forming the compact 
bundle of the posterior nerve root give no indication of a constriction zone, but are 
continued within the cord for a considerable distance, retaining their neurilemma 
sheath and nucleus and, as in the anterior roots, carrying in, as it were, round each 
fibre a layer of the pia, with which the neurilemma sheath usually blends at the ring 
of Obersteiner. Individual fibres can be traced through the posterior root-entry zone 
almost to the edge of the posterior horn, and reflex collaterals, with this structure, as 
far as the base of the anterior horn. The extra-medullary root gives the impression of 
having been carried right into the cord substance and, intra-medullary, differs only in 
showing an increased interfibrillar tissue with more numerous nuclei. Between, and 
on either side of, the longitudinal entering strands cross-sections of fibres show an 
involvement in the fibrosis, as if fine fibrils of connective tissue had enclosed them in 
