350 THE LUMBAR ENLARGEMENT OF THE SPINAL CORD. 
(2.) Anterior and posterior roots which meet in cells near the central part of the 
gray substance. | 
(3.) Anterior and posterior roots which are directly continuous. 
4. That bundles of anterior roots are connected with those above and below, by 
looped fibres proceeding from cells which some of the roots enter; these fibres leaving 
the gray substance, and passing sometimes upwards, sometimes downwards through the 
anterior columns, finally curving inwards to join some other bundle of anterior roots 
with which they pass into the gray substance. 
9. That thus fibres from nerve-cells after passing upwards through the longitudinal 
white columns, do not all continue onwards to the brain, but most of them re-enter 
the gray substance at a greater or less distance from the point of exit, sometimes prob- 
ably becoming again connected with cells, and again emerging from these as longitu- 
dinal fibres. 
6. That the processes from a single nerve-cell, whether in the anterior or posterior 
cornu, do not necessarily all pass into the same bundle of roots, but often pass into 
three or four different bundles; a cell process also sometimes sending branches into 
different bundles. Thus we may have sensitive impressions from different parts of the 
surface conveyed to one cell, and motor impulses distributed from one cell to different 
points. 
T. That all the anterior and probably all the posterior roots enter the gray Substance, 
though the posterior roots often pass into the cornu at a considerable distance from 
their first entrance into the cord. 
8. That most of the fibres from the posterior roots, after traversing the posterior col- 
umns, are collected into transverse bundles, traversing the substantia gelatinosa in a 
slightly ascending course; after passing through which they curve downwards (some- 
times upwards), forming, by the longitudinal course which they then maintain for some 
distance, a very interesting series of longitudinal bundles, which I have called longitudi- 
nal columns of the cornua, standing in very close relation to the posterior vesicular col- 
umns of Clarke, with the cell processes of which many of their fibres are continur us. 
9. That some of the bundles which traverse the substantia gelatinosa do not pass 
into the longitudinal columns of the cornua, but proceed directly across the gray sub- 
stance, becoming continuous with the anterior roots. 
10. That the posterior white columns are composed almost entirely of the posterior 
roots, which merely traverse them before entering the gray substance. They appear, 
however, to receive a few fibres from cells situated on the extreme margin of the poste- 
rior cornua, and some more or less longitudinal fibres from the looped recurrent 
bundles. 
