THE STRUCTURE OF THE SPINAL CHORD. 
609 
inch in diameter. It is situated much nearer the anterior than the posterior surface 
of the chord* * * § . 
The nerve-vesicles however are few in number, and scattered irregularly through 
the grey substance. They are not, as in some other regions, collected into large 
masses, but are most numerous in the anterior cornua, at the extremities of which 
three or four may be seen closely grouped together. 
Nature and Arrangement of the Nerve-fibres in the Grey Substance of the Spinal Chord. 
The nerve-fibres in the grey substance of the spinal chord are mostly of the white 
tubular kind, and of variable but small average diameter'!'. With regard to direction, 
they may be divided into two classes, — transverse and longitudinal. 
Transverse Fibres. — These again may be divided into two orders, — antero-posterior 
and latero-transverse. 
Antero-posterior Fibres. — On each side of the middle line, in the posterior grey sub- 
stance, are several large bundles of fine nerve-tubes, which take a transverse direction 
from behind forwards (see Plate XX. fig. 1). These bundles maybe traced through the 
posterior white columns, partly into the roots of nerves which arise in the same ver 
tical (in Man, horizontal) plane, and partly into others above and below them. They 
are convex towards the middle line, but on approaching the anterior cornua, they break 
up into smaller bundles, which interlace with each other and form a coarse network, 
in the meshes of which the nerve-vesicles are contained. Many of these nerve-tubes, 
both singly and in bundles, extend outwards into the antero-lateral white columns^. 
Many of them, also, appear to be continuous with the anterior roots of the nerves ; but 
whether they be so or not, the anterior and posterior roots are mingled together in 
the network above mentioned^. Between the spinal canal and the anterior median 
* As stated by Stilling and Wallace, it extends uninterruptedly through the whole length of the medulla 
spinalis. In many preparations that I have by me of the filiform extremity of the chord, where it measures 
less than a line in diameter, the spinal canal is even larger than in other regions. 
•t By Drs. Stilling and Wallace they are described as grey fibres, but seem to have been examined under 
strong pressure. Moreover, they ought to be examined in a perfectly fresh state, as spirits of wine considerably 
alters their appearance. 
+ After nearly reaching the circumference of the chord, they appear to form with each other a series of loops of 
various sizes ; but of this arrangement I cannot speak with any confidence, for it is seen only in a section of a 
perfectly fresh chord, and under strong pressure, to which the appearance may be due. Stilling (Textur des 
Riickenmarks, p. 21) also states that the transverse (so-called) grey fibres form loops at the periphery of the 
chord, but since he made use of strong compression, his statement is open to the same objection. 
§ This description corresponds, in some measure, with that given hy Dr. Stilling (Ueber die Medulla Ob- 
longata, p. 4), who states that the posterior nerves, after forming loops within the grey substance, become con- 
tinuous with the anterior roots. I have never seen loops such as he describes, but the rest of his statement is 
probably correct ; for although it is impossible to trace any single fibre from the posterior to the anterior roots, 
it is nevertheless certain that the latter are continuous in the grey substance with bundles w'hich proceed from 
the former. According to Stilling, therefore, the anterior and posterior roots of the spinal nerves are united 
in the grey substance by intervening grey fibres, since all the transverse fibres are described as such ; or to use 
