9 
that they cannot be traced further. Above this spot the 
papilla is a little thickened and the tissue more granular, 
and hence it is not to be wondered at that great difficulty 
should have been experienced in demonstrating the further 
course of the nerves, or that many different views should be 
entertained upon the oft-debated question of the mode of 
ending of nerves in this situation ; but it is most certain that 
the fibres do divide and subdivide into finer and much more 
transparent fibres at this point, and that these again divide 
and subdivide and form an elaborate plexus in the summit of 
the papilla, which has not been before described. 
By reference to my figures, the arrangement, which is not 
easily described with accuracy, will be at once understood, so 
that a minute description of it would be superfluous. 
Above the plexus c (PI. II, fig. 3), and below the epitlie- 
lium-like organ at the summit of the papilla (a), is a layer ( b ) 
which appears to be composed of granular matter. In my 
most perfect specimens, however, this “ granular layer,” 
when examined by very high powers under the influence of 
a good light, is seen to consist of a plexus of extremely fine 
fibres which interlace with one another in every direction, 
but which pass from the plexus above to the epithelium-like 
nervous (?) organ upon the summit of the papilla (PI. I, 
fig. 2). I believe this granular appearance to result from 
the extreme delicacy and fineness of the nerve- fibres at this 
part of their course. In like manner the “ granular matter ” 
seen in the grey matter of the cerebral convolutions and that 
of the retina, results mainly from the breaking down of very 
fine and delicate nerve-fibres, which undergo disintegration 
very soon after death, unless they are subjected to special 
methods of preparation. 
Of the existence of the elaborate network of nerve-fibres 
with the large nuclei, represented in PI. II, fig. 3, c, there 
can be no question whatever ; but there may be some differ- 
ence of opinion regarding the exact relation of the very fine 
nerve-fibres at the summit of the papilla, to the peculiar cells 
which surmount it, and the ultimate ramification of the 
fibres of the elaborate plexus just described. However, there 
are but two possible arrangements : 
1. That the nerves form a network of exceedingly fine 
fibres upon the summit of the papilla, upon which the bases 
of the epithelium-like cells impinge. 
2. That the very fine nerve-fibres are really continuous 
with the peculiar and epithelium-like cells ; in which case 
these bodies must be regarded as part of the nervous 
apparatus. 
