342 > THE LUMBAR ENLARGEMENT OF THE SPINAL CORD. 
From what has gone before, it appears that there are probably, as ZS? origin, 
the three following classes of nerve-roots, viz.: 
(a) Anterior roots which arise from or terminate in anterior cells. 
e | (6) Posterior roots = 7 » " * posterior cells. 
2d. Anterior and posterior roots which meet in cells in the central part of the cord. 
3d. « > = * which are directly continuous, i. e. unconnected with any cells in the cord. 
The first class consists of nerve-roots which are united, if at all, through the medium 
of deeper lying cell-groups, those of the last two classes being more directly continu- 
ous. I am, however, very far from intending to imply any supposed difference of func- 
tion between these classes, for I am very strongly convinced that the function of cell 
and fibre is everywhere the same; and one of the principal objects I have had in view 
in the above classification has been to show how closely anterior and posterior roots 
are connected, and how nearly they come to having a common origin. 
(c.) The Connection of the Cells with the Longitudinal W hite Fibres. —'This connection 
can be very plainly made out in the anterior and antero-lateral columns, between cells 
situated just at the outer margin of the anterior cornu and the adjacent longitudinal 
white fibres, these latter being seen to be direct continuations of cell processes, passing 
in a transverse direction a greater or less distance before turning upwards. This 
course is represented in Fig. 5, a, a; the bundles formed by these ascending fibres are 
seen at a’. Schröder van der Kolk gives an accurate figure of this derivation of the 
white fibres (loc. cit., Fig. 5), agreeing with Bidder that all the longitudinal fibres of 
the anterior and lateral columns arise from cells. Stilling, on the other hand, main- 
tains “that the whole white substance of the spinal cord (like the separate columns) 
has a double origin, peripheral and central." 
The whole subject of the constitution and origin of the white columns needs careful 
investigation, more so, perhaps, than any other part of the cord; my own observations 
have led me to the following views, which are, however, merely an outline of the sub- 
ject. The anterior and lateral columns, apart from the anterior roots, are only partially 
derived from the cells of the anterior and posterior cornua, some of the white longi- 
tudinal fibres seeming to be direct continuations of the posterior roots, after these have 
passed through the gray substance; the posterior white columns are composed almost. 
exclusively of the posterior roots, a few fibres appearing to be derived from cell pro- 
cesses coming from the large cells, situated on the margin of the posterior cornu; 
what course these latter fibres take after leaving the gray substance I have been unable 
to determine definitely. | 
