THE STRUCTURE OF THE SPINAL CHORD. 
619 
I have now stated all that I have to say»at present on the subject of the spinal 
chord ; but if the observations contained in this communication be considered by 
the Royal Society to throw important light on its structure, they will be followed by 
others that I have made on the medulla oblongata and cerebellum. I cannot con- 
clude, liowever, without acknowledging the kind interest shown me, during these 
inquiries, by Mr. Solly, Mr. Grainger, and Dr. Marshall Hall. 1 am also much 
indebted to Mr. Frederick Brown (Member of the Microscopical Society) for several 
ingenious contrivances with which he kindly furnished me. 
Explanation of the Plates. 
PLATE XX. 
The Plates represent transverse sections of the spinal chord of the Calf, all of 
which, except the two last, were prepared according to the first method described in 
the paper. The same letters indicate the same parts in all the figures. 
Fig. 1. A section of the white and grey substances of the filiform extremity of the 
chord, scarcely more than one line in diameter ; magnified 20 diameters. 
aa. Posterior white columns ; hh, Antero-lateral columns of one side ; 
c. Posterior lateral fissure, which Separates the posterior from the antero- 
lateral white columns ; d. Anterior median fissure ; d\ Posterior median 
fissure ; e. Foramen ; ff. Anterior cornua ; g". Substantia gelatinosa. On 
each side of the middle line are seen antero-posterior bundles of fine tubu- 
lar fibres. 
Fig. 2. A section of the grey substance of the chord about an inch higher up ; mag- 
nified 20 diameters, h. Arched band of tubular fibres; i. Light space sur- 
rounding the foramen and composed of a circular layer of fine fibrous 
tissue ; the margin of the foramen is set with columnar epithelium ; 
c". Rudiments of the posterior cornua; on each side the substantia gelati- 
nosa is broad, but is gradually narrowed at the middle line; the dark or 
spongy portion of the cornua is seen projecting into it like the matted hairs 
of a brush. This appearance is caused by oblique sections of bundles of 
nerves and blood-vessels which enter the grey substance in a more or less 
longitudinal direction, or with various degrees of obliquity ; these, together 
with the bands of longitudinal fibres, are the chief cause of its opacity, and 
form the principal difference between its structure and that of the substantia 
gelatinosa. 
Fig. 3. Represents the same appearances higher up; magnified 20 diameters. The 
bundles of transverse commissural fibres are distinctly seen, as well as the 
decussating fibres in front of the spinal canal; the two dark oval masses 
