928 
MR. J. LOCKHART CLARKE ON THE DE\H:L0P]MENT OE 
In a foetal sheep of about If inch long, it was found that a considerable proportion 
of the nuclei or cells had increased in size, but in a variable degree. Many of them, 
were twice as large as those in the foetus of 1 inch, while others were still about the 
same size. Fig. 24, Plate XL VII. represents a small portion of the ganglion as seen in 
a transverse section of the spinal column and cord — that is, in the du’ection in which the 
nerve-roots enter and leave it. A great number of the nuclei or cells were also more 
diversified in shape ; they were round, oval, triangular, irregular in outline, and variously 
stellate. By processes of different lengths and degrees of fineness all of them were con- 
nected with each other, as well as with fibres of the nerve-roots ; and at the circum- 
ference of the ganglion this common network was continuous with the smTounding 
nucleated connective tissue, as at J, fig. 23, which represents a portion of the tissue 
connecting the outer part of the ganglion (a) with the lamina of the vertebra. Many 
of the round and oval nuclei evidently belonged to the connective tissue, and some 
few to the nerve-fibres which spread through the structure. The nerve-cells, although 
enlarged, had a smooth homogeneous aspect, and presented scarcely any traces of 
internal nuclei. Here and there, however, a faintly granular appearance was visible 
through their surface ; and in some cases, as at a, fig. 24, a rounded but imperfectly- 
defined body, resembling an indistinct nucleus, might also be observed. 
As development advanced, considerable changes were observed to take place in the 
appearance of the ganglion. At first, the principal changes consisted in an increase in, 
the size and granular structure of a large number of the cells, while their nuclei remained 
stiU indistinct (see fig. 24'^). Soon after, however, a striking alteration ensued both 
in the structure and form of the cells; fig. 25 represents a portion of the ganglion 
of a foetal sheep, about 3 inches long, transformed from those just seen in fig. 24'*'. 
Here the nuclei in the cells are large, well-defined, round or oval, and contain one, two, 
and in some instances three globular nucleoli, surrounded by numerous granules. The 
cells to which they belong vary considerably both in size and shape. The majority, 
however, are perfectly pyriform or cup-shaped, their tapering ends pointing in different 
dh’ections, while the broader end of each is occupied, or as it were closed, by its nucleus.. 
According to the position in which they lie, and their different degrees of foreshortening, 
in reference to the observer, they appear either round, oval or pyriform. Sometimes 
several of them lie side by side in a similar position, and are continuous by theu taper- 
ing ends with a corresponding series of branches from one nerve-fibre. Lodged in the 
spaces between them are a number of small nuclei, of an angular, oval, or elongated 
form, and resembling those which belong to the sheath of the ganglion (see figs. 25 
& 28). When exceedingly thin sections were very carefully examined under a sufficient 
magnifying-power, it might sometimes be observed that the nerve-fibres, in then* course 
through the ganglion, divided into branches,, which became continuous with the pro- 
cesses of the cells ; and when the section was carefully broken up into minute frag- 
ments by means of fine needles, these appearances were found to be universal. The 
nerve-fibres were then frequently seen to consist of bundles of delicate fibrillse, each of 
