RESEARCHES INTO THE CAUSES OF BLINDNESS. 343 
Membranes of the Eye . — The sclerotica has not undergone any 
particular alteration except that its texture appears to us scarcely 
so dense or close. It is the choroid membrane and the retina 
which suffer chiefly from the attacks of the disease. The former 
has lost its brilliant silvery hue and become soft and black, and 
the slightest touch is sufficient to detach it from the internal sur- 
face of the sclerotica. The retina can scarcely be said to exist at 
all: it is often very difficult to recognize it, because in endeavour- 
ing to separate it from the choroid membrane this latter absorbs it 
in the black pulp which it forms. Nothing is so common, after 
having emptied a healthy eye, as to be able to separate the retina 
in a perfect state from all its adhesions, and to see it suspended in 
the circumference of the opening that admits the passage of the 
optic nerve. We have vainly endeavoured to do so in diseased 
eyes. 
Such are the morbid lesions found in eyes attacked with blind- 
ness, but which have still preserved the integrity of all their con- 
stituent parts. 
In the second class we have comprehended those lesions in 
which loss of sight has been accompanied by atrophy of the organ 
of vision. 
A careful study of this fatal termination enables us to distinguish 
two kinds of atrophy, — the one resulting from an over-accumulation 
of fluid in the cavities of the eye, and the other induced by a sui 
generis irritation, acting gradually, without increasing the humours 
generated by the eye. 
In the former case we generally find the scar of the wound 
through which the fluid escaped when it was contained in the 
chambers of the crystalline and vitreous humours. The bulb has 
disappeared into the bottom of the orbital cavity — its exterior parts 
are contracted together — the nictitating body is thrown forward — 
the muscular parts fall — the lachrymal gland is diminished in size — 
the conjunctiva, uniformly the seat of irritation, as is rendered 
evident by the size of the Meibomian gland, secreting an abundant 
purulent discharge, which flows from the edges of the eyelids. 
In the second class the various parts of the natural eye retain 
their respective places, but are diminished considerably below their 
normal size, and the humours, which are not so abundant, are some- 
what of the consistence of pus. The pupillary opening is contracted. 
The crystalline — which does not exceed a large pea in size — is 
hard and opaque. The vitreous humour, which is likewise diminish- 
ed, is of a greyish hue, and resists pressure. In the anterior chamber 
a pulpy substance is frequently found, similar to that which, in a 
natural state, constitutes the crystalline. When the eyes have 
undergone this transformation, the secretory irritation of the con- 
