Histology of tJie Eye. 
C Monthly Microscopical 
Journal, Nov. 1, 1869. 
appearance under a low power, is therefore preferable to tliat of 
grey vesicular or grey nervous layer, whicli gives a wrong idea of 
essential composition. 
The cells of the ganglionic layer possess a very distinct roundish 
nucleus, imbedded in a pale and very soft protoplasm, about which 
there is not generally any distinct cell- wall perceptible. I believe 
that all the cells are branched. The outer branches, which are the 
more numerous, run outwards into the granular layer to join those 
coming inwards from the inner granules, while their inner branches 
join the bundles of optic nerve-fibres. 
These last radiate in a plexiform manner from the optic nerve 
entrance. Where there is a fovea centralis, as in men, apes, some 
birds, and reptiles, the nerve-bundles are so distributed that those 
only destined for the fovea and its surrounding maculae pass directly 
to it ; while those bundles going to more distant parts beyond the 
fovea arch around it. With some exceptions, the nerve-fibres are 
devoid of medulla. In our own eyes, this ceases at the lamina 
cribrosa; and only pale fibres, equivalent to axis-cylinders, with 
perhaps an investment of the sheathing membrane, are produced 
into the retina. 
The connective-tissue frame, which supports and holds together 
the nervous elements, consists of three segments. First, there are 
the two membranes ; — the outer limiting membrane, which I have 
already described ; and the membrana limitans interna, which some 
identify with the hyaloid capsule of the vitreous humour, but which 
I regard as a distinct membrane. This distinctness cannot be 
always demonstrated at pleasure; but I believe it to be a fact, 
because I have found the two membranes separated by inflam- 
matory effusions, and because in the eyes of a Burchell's zebra, for 
which I was indebted to the liberality of the Zoological Society, I 
found a beautiful pavement of epithelium on the outer surface of 
the capsula hyaloidea. The second member of the connective sub- 
stances is a system of stout pillar- like fibres, which arise by ex- 
panded wing-like roots from^ the outer surface of the limitans 
interna, and traverse vertically all the layers in a direction radial 
from the centre of the eye-ball. These are the fibres which, when 
originally discovered by H. MuUer, were believed by him to link 
the percipient elements on the outer side of the retina — the rods 
and cones — with the conducting optic-nerve fibres at the inner 
surface of the retina, an error which he himself was one of the first 
to correct. They form a frame, which mechanically binds together 
the several layers in their order. Lastly, the retina contains a 
large amount of interstitial connective tissue, which is accumulated 
in larger quantity between the inner and outer granules, and between 
the inner granules and ganglionic layer, but which also pervades, 
in smaller quantity, all the nervous layers except the bacillary. 
