52 
Structure of the 
t Monthly Microscopical 
Journal, July 1, 1869.. 
is the hyaloid canal, which gave passage, in the emhryonic eye, to 
the hyaloid vessels. It is not a constant structure of the adult 
vitreous humour, and in old age not a trace of it can be found. In 
some cases, however, it is not only present in the adult, but it 
remains patent through the whole of its extent, and in such cases, 
after the vitreous body has been macerated, is often seen to contain 
opaque granular matter, as if it still conveyed, during adult life, 
nutriment for the crystalline lens. The hyaloid canal has a dia- 
meter about that of a common probe, and, unlike the same structure 
in its primitive condition in the foetus, it gives off no branches to 
the vitreous humour. 
(h) Arising at right angles from, and surrounding the inner 
surface of, the zonula Zinnii, are eight or ten membranous circles, 
placed the one within the other ; each circle, on close examination, 
being seen to be made up of a series of segments, overlapping and 
uniting by their edges — the arrangement not being unhke the 
origin of the leaves of a leaf-bud from a circular disc. Proceeding 
from this origin, these membranes take a course backwards to the 
entrance of the hyaloid canal, and in their course split horizontally 
the entire circumference of the humour into innumerable shallow 
cells, placed with their flat surfaces to the hyaloid membrane, which 
build up, layer upon layer, the sides of the vitreous body around 
the antero-posterior axis of the eyes as a centre (Figs. 2 and 3). 
Fig. 3. 
Arrangement of the membranous strata 
within the human vitreous humour 
(natural size). A, Crystalline lens ; 
B, Zone of Zinn ; C, Hyaloid mem- 
brane; D, Cortical portion of the 
humour; E, Medullary portion of the 
humour ; F, Hyaloid canal ; G, Ra- 
diating fibres. 
Origin of the membranous 
strata from the zone of 
Zinn (natural size). A, 
Crystalline lens ; B, Ex- 
treme border of zone. 
These membranes are made up of the strong, smooth, fibrous 
elements already referred to under the microscopic examination of 
the humour. When they are examined individually with the naked 
eye by the aid of the direct rays of the sun, they are seen to consist 
of a flimsy network of fibres, which, for want of a better name, 
I have called membranes, though they scarcely admit of being so 
classified ; and though I have described as cells the compartments 
which the membranes enclose, they are incapable in any degree of 
limiting the fluid of the humour. The more superficial membranes, 
