im. J. L. CLAEKE ON THE OEET SUBSTANCE OE THE SPINAL COED. 441 
rior roots, or through a fissure containing a blood-vessel ; or two contiguous bundles of 
the posterior roots, as they pass out from the gelatinous substance, are accompanied by 
the processes of a crescentic cell, which occupies the curve between them (see fig. 1, 
Plate XIX.). And beyond the j)oint of the cornu, a variable number of others, of different 
shapes and sizes, may be seen amongst the networlc of blood-vessels and fibres, which is 
formed, as already stated, around separate fasciculi of the posterior and lateral columns. 
They occupy the angular interspaces or partially embrace the fasciculi, and send between 
them their processes, which contribute to form the network (b, b, fig. 1). 
(b) The small cells abound in every part of the gelatinous substance. They are round 
or oval, somewhat pyriform, fusiform, or angular, and give off two processes or more. 
Fig. 46, Plate XXII. a, J, c, represents them magnified 350 diameters. They vary con- 
siderably in size, and many are nearly as minute as blood-disks^. The largest of them 
contain distinct nuclei. Near the border of the posterior columns, the oval and fusi- 
form variety, like those of the first set, are elongated transversely, longitudinally, and 
obliquely ; but through the rest of the gelatinous substance the longer axes of many, 
as well as their processes, are parallel to the antero-posterior fibres that form the posterior 
roots of the nerves, with which they are apparently continuous (fig. I, Plate XIX.). 
(c) The cells of intermediate size, like the first set, which they closely resemble in 
shape, are found chiefly near the verge of the posterior columns. Some are so exceed- 
ingly fusiform that they appear like gradual dilatations in the course of the fibres, but 
still they are true cells. 
There can be no doubt whatever that a great number of the smallest cells of the 
gelatinous substance belong to the connective tissue. This tissue extends as a fine 
network from the border of the grey substance, through the white columns as far as the 
surface of the cord, where it forms a layer of variable thickness, in which its fibres run 
circumferentially, and return at intervals to rejoin the network in the white substance. 
Now in very delicate preparations which I lately made of the spinal cord of the Calf 
between three and four months old, I discovered that in every part of the white columns 
the connective tissue between the primitive nerve-fibres abounds with both nuclei and 
small nucleated cells, many of which are quite equal in size and similar in character to 
numbers of those which are found in the gelatinous substance ; but on account of their 
position, some of them are more diversified in shape. They are more or less round or 
oval, pyriform or club-shaped, angular, fusiform or crescentic, and lie in the interspaces 
between the nerve-fibres, sending out fine processes in difierent directions to join the net- 
work of connective tissue. Frequently a crescentic cell half encircles a primitive nerve- 
fibre, and forms a swelling or knot around one side of its sheath. Fig. 48, Plate XXII. 
represents the appearance of some of these nucleated cells and free nuclei. There is no 
difference in structure between them and the smallest of those in the grey substance ; 
indeed from this substance an wninterru/pted layer of cells and nuclei, of an apparently 
* Care must be taken not to confound these minute cells with the cut ends of small blood-vessels : a 
mistake not at all unlikely to occur where they are not very distinct and well-defined. 
