CHORD, WITH FURTHER INVESTIGATIONS INTO ITS STRUCTURE. 353 
I cannot agree with the statement of Kolliker, that all these fibres continue the 
same course within these columns in the direction of the brain ; for it is certain, as 1 
have already observed, that many of them not only pursue a descending course, but 
that others which actually ascend re-enter the grey substance to form loops. It is 
certain, also, that of the anterior roots in particular, the fibres, on reaching the grey 
substance, diverge in a direction as much downwards as upwards. 
It seems therefore that many of the fibres which belong respectively to the anterior 
and posterior roots, in different regions of the chord, terminate there by forming with 
each other a series of loops, partly within the grey substance, and partly after 
extending through the latter into the white columns ; and that these loops are of 
various sizes and lengths. Nor is it improbable that some of them may reach even 
as far as the brain, since it is well known that the formation of loops is at least one 
mode in which nerve-fibres terminate there. I am far from denying, however, that 
a portion of the roots may be connected with the vesicles of the chord. 
Does the grey substance of the chord transmit impressions to and from the brain ? — 
Stilling divided, in a living animal, the anterior white columns through their whole 
thickness, and found that voluntary power was still conveyed to parts below the 
section ; but when the incision extended deeply into the grey substance, all voluntary 
movements were interrupted. From this experiment he infers that the grey substance 
alone is the conductor of voluntary power from the brain to the anterior roots ; and 
the means of communication he explains by a system of fine longitudinal fibres which 
he found in the anterior grey substance. I thought formerly that I also had seen such 
fibres in comparatively small numbers ; but further and more careful observation has 
led me to the conclusion, that excepting those in the substantia gelatinosa and those 
near the border of the substantia spongiosa, there is no regular system of fine longi- 
tudinal fibres in the grey substance. In looking for such fibres I have always selected 
a perfectly fresh chord. An exceedingly thin section, which by practice may be 
made with a very sharp instrument, was carefully laid on a glass slide and treated 
with acetic acid, which increases its transparency without producing any material 
alteration in the appearance of its fibres. It was then covered with thin glass, and 
examined, without any pressure, under sufficiently high powers. In such a section, 
fibres of various diameters — many exceedingly fine — may be seen to cross each other 
in every direction, but not in one direction more than another. It is probable that 
even the longitudinal fibres of the substantia gelatinosa are not continued, indivi- 
dually, as far as the brain, but pass out at intervals into the white columns, since 
their number, as well as the breadth of the substantia gelatinosa, does not increase 
regularly from below upwards. I believe that they are all derived from the fine 
bundles of the posterior roots*. 
* Kolliker supposes that the nucleated fibres of the substantia gelatinosa, described by Remak, are pro- 
cesses of the nerve-vesicles ; but these processes contain no nuclei. It is more probable that the fibres of 
Remak are really small blood-vessels, which have precisely the same appearance, and of which a large number 
enter with the posterior roots and pursue the same longitudinal course in the substantia gelatinosa. 
3 A 2 
