THE EYE OE THE OX. 
221 
Fig. 10. 
iO- 
Fig. 11. 
so named from its similarity to horn ( corneus , horny); is com- 
pared in shape to a watch-glass; it is perfectly transparent 
(in Plate XL, figs. 1 and 3, extending from b to b). 
Although perfectly transparent; even as glass (that 
is, to the naked eye), it has a fibrous structure 
(fig. 10), the fibres being very even and regular, 
and running parallel to each other ; between the 
fibres are a number of tubes, pursuing also a 
regular, parallel course. In front of the cornea is 
a thin elastic layer, covered by a transparent cuticle; and 
behind the cornea is another elastic layer, which passes on 
and terminates in the iris. These elastic 
membranes preserve the proper convexity of 
the cornea (in fig. 3 the situation of these 
lamina) may be seen ; in fig. 1 1, their 
structure is shown). 
The sclerotic (shier os, hard) is an exceed- 
ingly strong structure directly continuous 
with the cornea, and investing the eyeball 
completely, except where the cornea comes 
in (extending from b round by c, c, c, to b 
again, in Plate XI., fig. 3). It is about W 
of an inch in thickness, and its fibres (Plate XI., fig. 4) 
are not, as those of the cornea, parallel, but run in con- 
trary directions, mostly crossing each other at right angles ; 
hence the dense and strong nature of this covering. What is 
popularly known as the white of the eye, is a part of the 
sclerotic, covered by a thin mucous membrane. To the 
sclerotic are attached the various muscles that move the 
eyeball, and behind, it is perforated for the passage of the 
optic nerve (Plate XI., fig. 3, n). 
Looking at Plate XI., fig. 3, it will be observed that at h is 
a part coloured yellow : this consists of two structures, one 
behind the other ; the first is called the ciliary ligament, the 
second, the cihary muscle. By means of the ciliary ligament 
(a ligament being something that binds and connects parts 
together : ligo, to tie or bind), the iris (Plate XI., fig. 3 , f, f) is 
attached to, and suspended from, the sclerotic. On removing 
the cornea and sclerotic, during which we must separate the 
latter from the cihary ligament, we obtain a body similar to 
Plate XI., fig\ 2. We notice that the eye has lost its high- 
arched form : this is due to the fact that the semi-fluid material 
forming the bulk of the eye has now but very weak structures 
surrounding it, and therefore tends to flatten downwards. 
The choroid coat of the eye (like the chorion, which is a 
vascular membrane of peculiar formation, chorion, eido-s), is 
that next beneath the sclerotic; it extends from the entrance 
