920 
ME. J. LOCKHAET CLAEEIE ON THE DEVELOPJIENT OF 
fig. 8, Plate XLVI.). The anterior roots {g) are attached to the anterior column, which 
they traverse transversely inward to reach the anterior cornu (/), within which their 
fibres diverge and cross each other in difierent directions. A large number proceed; 
backward along the lateral part of the cornu, some of them running in succession 
outward to the lateral column (A'), while the rest reach the triangular group of nuclei 
just pointed out, vrithin the posterior angle of the cornu. Another set of fibres run more 
directly backward, through the central part of the grey substance (/), where they join 
in the general network, and appear as represented in fig. 11, Plate XLVII. ; while 
some curve inward to decussate, in front of the canal, with their fellows of the opposite 
side, in company with others proceeding forward and inward around the canal fi’om the 
^ostenor grey substance. (See also fig. 3, Plate XLV.) 
The posterior roots (fig. 8, d, Plate XLVI.) have no immediate connexion with the 
lateral columns, and are attached solely to the posterior, through which they diverge in 
a direction backward and inward to reach the grey substance {I h). On entering this 
substance many of them evidently become finer by subdivision, and contribute to form 
the network by which the nuclei are connected. Pig. 10, Plate XLV. is a faithful 
representation of a very thin transverse section near the extremity of the posterior coma, 
through which the roots {d) are entering ; at h they are seen to become continuous with 
the general network. In the same way many of the fibres of the posterior columns are 
connected with nuclei of the grey substance. (See fig. 15, i, Plate XLVII.) 
In foetal sheep of 3 and 4 inches in length, there was no remarkable alteration in the 
shape and disposition of the grey and white substances in the region corresponding to 
fig. 4; nor was there any great difference in the appearance or arrangement of the 
constituent elements. Fig. 13, Plate XLVI., represents a transverse section of one, and 
part of the other, lateral half of the spinal cord, near the middle of the lumbar enlarge- 
ment, of a foetal sheep, 4 inches long ; and fig. 14 shows a similar section of the middle 
of the lumbar enlargement of a foetal ox, 5 inches long. Here we see that nearly one- 
half of the posterior grey substance still consists of a dark layer of closely aggregated 
nuclei, which differ but little in size and general appearance from those of section 4, 
Plate XLV. This dark layer constitutes the cajgut cornu posterioris. Fig. 15, i, 
Plate XLVII. is a longitudinal section of it near its outer border, or the posterior 
extremity of the cornu, where it is overlaid and crossed in different directions by the 
decussating fibres of the white column. As the posterior (/ J, fig. 14) merges into the 
anterior grey substance {f), the nuclei become larger, while the network which supports 
them becomes coarser and looser (ii, fig. 15, Plate XLVII.). In the posterior part of the 
section, the very irregular and granular meshwork of fibres appears to extend nearly 
equally in all directions ; but towards the anterior part (opposite ii) the meshes have a 
tendency to elongate in a direction forward ; while many of the nuclei are elongated in 
the same direction, and have tapering granular masses extending from their ends. 
These latter appearances, however, are more conspicuous on the inner side of the coma, 
nearer the median line. On proceeding forward, the network assumes the peculiar 
