THE SPINAL COED IN MAN, MAMMALIA, AND BIEDS. 921 
honeycomb structure already observed in "section 4, and represented at x, fig. 12, 
Plate XL VII. Here, however, the layer is deeper, but variable in depth. Fig. 15, iii, 
Plate XLVII. is a portion of a longitudinal section, behind-forward, through this layer of 
large cells of the anterior cornu (ww, fig. 14, Plate XLVI.). It will be remarked that 
these more or less globular cells are closely grouped, and frequently in actual contact ; 
that in many instances they are seen to be filled with the granular material surrounding 
their nuclei ; and that the nuclei themselves are sometimes larger than those in other 
parts of the anterior grey substance, and contain each either one large globular nucleolus 
or two. With the general network of this layer the anterior nerve-roots may be seen to 
be continuous. 
In foetal sheep of 6, 7, and 8 inches in length, further changes were observed to take 
place in the grey substance, but they were limited chiefly to its posterior and middle 
portions. In the cajput cornu posterioris, the nuclei, although still aggregated in vast 
numbers, were comparatively less numerous and more widely separated from each other 
than in fig. 15, and somewhat larger; the network of fibres by which they were con- 
nected was also coarser and looser ; while a complete system of transverse, longitudinal, 
and oblique nerve-fibres were very readily distinguishable. 
In the middle portion of the grey substance, that is, between the caput cornu (1 5, 
fig. 13, Plate XLVI.) and the gi’oups of large nerve-cells (w, w'), the coarse network 
already described and represented in fig. 15, ii, Plate XLVII. was now interspersed with 
a great number of cells, which difiered from each other both in size and shape (fig. 16, 
Plate XLVII.). The majority were fusiform in a direction before-backward, and either 
more or less wavy and sigmoid, or perfectly straight, with processes which extended 
occasionally to an amazing distance. In some cases, as at a, fig. 16, a fusiform cell was 
bent into the shape of a crescent, and formed part of the circumference of an oval or 
circular space. In other cases it was converted into a triangle by giving off two pro- 
cesses from one end, which became broader, and embraced, as before, part of the cir- 
cumference of an open space (d, fig. 16). In many of these cells, especially of the 
smaller kind, the nuclei were only faintly, or not at all, observable. 
The groups of large nerve-cells (w, w') had undergone scarcely any appreciable change, 
and presented nearly the appearances represented at iii, fig. 15. 
With regard to the changes which ensue in the structure of the cord on approaching 
the period of birth, I shall confine my remarks chiefly to those particular points which 
relate to the development of its constituent elements. During these successive changes, 
the gelatinous substance becomes more and more conspicuous as a distinct lamina around 
the end of the caput cornu. Along its margin the peculiar nerve-cells observable in the 
adult are gradually developed, after the manner of those already described in the middle 
of the grey substance (fig. 16, Plate XLVII.); while its arciform, transverse, oblique 
and longitudinal fibres increase in number in a corresponding proportion. Coincident 
with this development of the gelatinous substance, the nuclei in the dark and inner part 
of the caput cornu become less numerous, while its transversely-radiating, longitudinal, 
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