It is interesting to see how old questions are incidentally settled in
the course of these new investigations. Thus, Mr. Clarke's dissections,
confirmed by preparations of Mr. Dean's which I have myself examined,
placed the fact of the decussation of the pyramids--denied by Haller, by
Morgagni, and even by Stilling--beyond doubt. So the spinal canal, the
existence of which, at least in the adult, has been so often disputed,
appears as a coarse and unequivocal anatomical fact in many of the
preparations referred to.
While these studies of the structure of the cord have been going on, the
ingenious and indefatigable Brown-Sequard has been investigating the
functions of its different parts with equal diligence. The microscopic
anatomists had shown that the ganglionic corpuscles of the gray matter of
the cord are connected with each other by their processes, as well as
with the nerve-roots. M. Brown-Sequard has proved by numerous
experiments that the gray substance transmits sensitive impressions and
muscular stimulation. The oblique ascending and descending fibres from
the posterior nerve-roots, joining the "longitudinal columns of the
cornua," account for the results of Brown-Sequard's sections of the
posterior columns. The physiological experimenter has also made it
evident that the decussation of the conductors of sensitive impressions
has its seat in the spinal core, and not in the encephalon, as had been
supposed.
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