ME. J. L. CLAEKE ON THE GEEY SUBSTANCE OF THE SPINAL COED. 448 
upon it* ; while in the cervical and lumbar enlargements they also extend, but in smaller 
numbers, through deeper parts of the cone. The bundles themselves are of different 
sizes and not exactly parallel, even in the same plane, but intersect each other at acute 
angles, and extend obliquely, at intervals, into the gelatinous substance; so that in a 
transverse section some of their divided extremities are more or less oval or elongated, 
and give to the posterior border of the cone, or lamina, an irregular or jagged outline, 
like the worn extremity of a brush (see fig. 2, Plate XX. D, on left side). 
h. The transverse fibres are continuous with the posterior roots of the nerves and 
longitudinal columns, and cross each other and the longitudinal fibres in a great variety 
of ways. Some of the roots, on reaching the base of the cone or caput cornu, return 
through it in loops to the posterior columns (see fig. 2, Plate XX. P, on right side) ; 
some become continuous with the longitudinal bundles, particularly on the outer side ; 
others cross them obliquely in opposite directions and run out on the one side through 
the lateral, and on the other through the posterior, columns ; while the rest proceed 
forwards through the cervix cornu, and in part escape through the posterior commissure 
to the opposite half of the cord. 
The oblique fibres, as may be inferred from the descriptions just given, are only con- 
tinuations of the transverse and longitudinal, at different angles and in different planes. 
c. Most of the cells are of the smallest and intermediate size. The majority are oval 
and fusiform — sometimes to a remarkable degree, and lie with their longer axes and 
then.’ processes in the direction chiefly of the oblique and horizontal nerve-roots, but also 
in the direction of the longitudinal fibres, with which they appear to be continuous. 
Amongst these, a few larger cells, from three to five in a transverse section of 
moderate thickness, are scattered at unequal intervals. They are more or less oval or 
fnsifonn, or irregular in shape, and give off from three to five processes, or perhaps more. 
Frequently one of these cells is found nearly as far back as the verge of the gelatinous 
substance ; but they mostly lie deeper. Sometimes they bifurcate around longitudinal 
bundles, which are probably accompanied by some of their processes, while the others 
may be traced to a surprising distance and in different directions, backwards, forwards, 
and laterally to the white columns. 
Having given the structure of the caput cornu posterioris, I shall next describe the 
cervix, or rest of the posterior grey substance, as it appears in the dorsal region, and 
then proceed to trace it both upwards and downwards, through the remaining length of 
the cord. In the dorsal region I shall describe it in considerable detail, and illustrate 
it by drawings of the greatest possible exactness, not only on account of its great interest 
and apparent importance, but in order that we may recognize its parts as the same 
during the changes which they undergo in passing through other regions. 
About the middle of the dorsal region in the spinal cord of the higher V ertebrata, the 
inner sides of the posterior cornua are in close contact along the middle line, or are 
* This layer of fibres I pointed out in my first communication on the Spinal Cord, Philosophical Trans- 
•ctions, 1851, Part II. p. 611. 
