350 MR. J. LOCKHART CLARKE ON CERTAIN FUNCTIONS OF THE SPINAL 
dinal course with the fibres of the posterior white columns, amongst which they are 
lost. It is impossible to say whether any of these longitudinal fibres are continued 
as far as the brain, or whether they ultimately reach the grey substance of the chord. 
It is also extremely difficult to trace the other fibres of these roots after they have 
reached the posterior grey substance. In some of my finest preparations, however 
they may be seen to interlace each other in a kind of network ; see Plate XXI . - 
large proportion diverge abruptly in various directions, so that in any section t ey are 
always divided. Many of them, both singly and in small bundles, may be observed 
to form loops by returning to the white columns. 
Of the Anterior Roots.— anterior roots of the spinal nerves, as I formerly 
described them, traverse the anterior part of the antero-lateral columns in distinct and 
nearly straight bundles. Plates XXIII. and XXIV. A, A, A, A. They form tio inter- 
lacement with each other, like the posterior roots, until they reach the grey substance. 
Here their fibres diverge in every direction, like the expanded hairs of a bins . ome, 
near the margin, are easily seen to form loops with those of contiguous bundles; 
others run outwards to the lateral columns, and inwards to the anterior columns 
after decussating in the anterior commissure with corresponding fibres from the 
opposite side. A large number diverge equally downwards and upwards for some 
distance in the grey substance, while the remainder pass more deeply backwards 
and are lost. In no single instance have I seen any portion of these roots take a 
longitudinal course on directly entering the anterior white columns. 
But besides the transverse bundles which form the anterior roots, a continuous 
system of exceedingly fine transverse fibres may be seen to issue from the^ anterior 
grey substance. They pass through, nearly all at right angles to, the anterior white 
columns, and disappear as they proceed towards the surface of the chord; but as 
many of them may be observed to turn round and take a longitudinal direction, it is 
probable that at the points where they disappear they all follow the same course. 
Within the grey substance they wind about and are gradually lost, mingling v ith 
the fibres of the anterior roots, and with those proceeding from the fine bundles ot 
the posterior roots, which, perhaps, are continuous with them. 
It may then, I think, be fairly laid down as a well-established fact, that nearly all, 
if not the whole of, the fibres composing the roots of the spinal nerves, after passing 
through the anterior and posterior white columns of the chord, proceed at once to 
its grey substance ; and that if any of them ascend directly to the brain, it must be 
those only oi i\\e posterior roots which run longitudinally in the posterior columns. 
That many excellent observers, with inferior means of observation, have arrived at 
a different conclusion on this extremely difficult subject, is not at all surprising. 
The opinions of Mr. Grainger are expressed in the following quotations from his 
excellent work on the spinal chord After the two roots have perforated the 
theca vertebralis, and so reached the surface of the chord, it is well known that then- 
fibres begin to separate from each other; of these fibres some are lost in the white 
