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MR. J. L. CLARKE’S RESEARCHES INTO 
Nor are the posterior columns of the chord connected by a transverse commissure ; 
for the posterior fissure, as stated, first, I believe, by Bellingeri*, reaehes down to 
the border of the grey substance, or rather, to the posterior border of its transverse 
commissure, which has been mistaken and described by Foville as a commissure 
between the posterior white columns, formed by their coalescence at the bottom of 
the fissure'l'. 
Of the Origin of the Spinal Nerves. 
Posterior Roots.—The bundles of fibres which form the posterior roots of the 
spinal nerves are much larger, but less numerous, than those of the anterior ; the 
fibres themselves, however, are mostly finer and more delicate They are attached 
immediately to the posterior white columns only^, which they traverse obliquely in- 
wards, interlacing and forming with each other an intricate plexus (see figs. 6 and 14). 
From this plexus straight and distinct bundles 1| enter the posterior cornua along their 
whole breadth, and cross the substantia gelatinosa both obliquely and at right angles; 
some being immediately continuous with fibres of the transverse commissure, while 
others, after plunging into the spongy portion of the cornua to unequal depths, break 
up and form a finer net-work which extends forwards into the anterior cornua : some 
of their fibres, after traversing the grey substance, pass out, as already described, into 
the posterior and lateral white columns. 
Anterior Roots. — These are attached exclusively to the anterior parts of the antero- 
lateral columns. They do not always enter the chord directly, or at the points of 
* De Medulla Spinali, pages 7 and 8. 
t He observes “Elle semble plutot la simple coalescence des deux faces laterales, reunies au fond du sillon.” 
Op. cit. p. 134. 
X 1 find that this statement coincides with that previously made by Remak (Muller’s Archiv, 1836) and by 
Henle, Allg. Anat. p. 669. 
§ I believe that this statement is directly opposed to the opinions of almost every anatomist, except Sir 
Charles Bell, that has written on the subject of the spinal chord ; and were it not undeniably proved to 
be true by the preparations which accompany this paper, I should feel some hesitation in coming forward to 
oppose so many eminent and recent authorities. According to Bellingeri (op. cit.) the posterior roots are 
attached to both the posterior and lateral, and the anterior roots to the anterior and lateral, white columns. 
Mr. Grainger and Mr. Swan join in referring the origin of both to the lateral columns only : the former 
observes (Spinal Chord, p. 30), “ I have never been able to trace any fibres from the nerves into the fasciculi 
composing the anterior and posterior columns.” A nearly similar statement is made by Dr. Todd. The two 
other most recent writers on the subject (Drs. Sharpey and Carpenter) have adopted the same views as Bel- 
lingeri. By Sir C. Bell (whose conclusion, however, was probably drawn from superficial examination) these 
roots are referred to the posterior columns only. “ Each nerve,” says he, “ has two distinct series of roots 
coming out in packets or fasces, one from the posterior column, and one from the anterior column, of the spinal 
marrow.” — Nervous System, p. 29, 4to. 
II The primitive fibres of most of these bundles are very small, their average diameter being about the 
y^^th of an inch ; a few very large tubules are found amongst the rest, and here and there is seen a slender 
bundle composed of fibres of larger average size. The anterior roots of the nerves within the grey substance 
are composed of fibres of more irregular size, and contain a much greater number of large tubes than those of 
the posterior roots. 
