348 THE LUMBAR ENLARGEMENT OF THE SPINAL CORD. 
larly near its border; others extend directly into the anterior white columns, and 
bending round, both upwards and downwards, are seen sometimes to re-enter the gray 
substance and form with each other a series of loops, and sometimes to continue a 
longitudinal course within the anterior white columns, amongst the fibres of which 
they become lost. Whether the latter also ultimately form broader loops with corre- 
sponding fibres from the gray substance, it is impossible to ascertain. But even if 
those which ascend in the anterior columns are continued upwards to the brain, one 
can scarcely avoid inferring that those which descend re-enter the gray substance, 
either to form loops or to become continuous with the fibres of the anterior roots, 
since the whole of the latter, as we shall presently see, proceed directly from the gray 
substance.”* This formation of loops near the border of the anterior cornu I have often 
noticed, and while I have no doubt that some of these loops found in the anterior 
columns are derived from the posterior roots, as stated by Clarke, I am convinced that 
a large portion of the looped fibres which are found in great abundance in the inner 
portion of the anterior white columns have a different origin, viz. from the cells of 
the anterior cornua, to which I have in some cases succeeded in tracing one or both 
ends of such fibres. + 
The Anterior Columns and Roots. — The anterior white columns contain the follow- 
ing elements: —(1.) The anterior roots which traverse them in a slightly curved 
ascending course; and (2.) Fibres which vary from longitudinal to every variety of 
curved course, often forming loops which may be traced a greater or less distance 
through the column. These loops are formed in the following manner: bundles of 
fibres, some of which arise from cells near the margin of the anterior cornu (Fig. 8, 
l, D), may be traced in a longitudinal section, descending obliquely until they. emerge 
from the gray substance into the anterior white column; here they continue the same 
general direction, finally curving round (as seen at k, k) and re-entering the gray sub- 
stance; in my description I have traced this bundle downwards, — it is obviously im- 
possible to say whether the fibres ascend or descend. 
Fibres belonging to these bundles may sometimes be seen to join cells at both ends 
* Philos. Trans. 1853, p. 349. 
t Stilling entirely denies the existence of looped fibres anywhere, with the singular criticism, that “ Clarke 
would allow that he had not followed the fibres in question continuously from the nerve-root on, through 
white and gray substance, into the white columns, and from these back again into the gray substance.” (Loc. 
cit, p. 1186.) This is the more extraordinary, since Clarke not only states that these fibres are seen to form 
such loops, but also figures them. (Philos. Trans. 1853.) It is by no means a very difficult thing to follow 
fibres quite across the cord in the smaller animals, such as the cat, from which Clarke's figure is drawn. 
