342 RESEARCHES INTO TIIE CAUSES OF BLINDNESS. 
The Anterior Chamber. — This part diminishes in size in an 
antero-posterior direction. The diminution results from the displace- 
ment of the crystalline lens, which bears on the posterior face of 
the iris, draws up before that organ, and so forms a convexity in 
the concavity. The fluid therein contained is, as we have already 
indicated, cloudy and thick, similar in consistence to gum-water, 
and the membrane that secretes it is covered with a thin plastic 
layer, extended over its walls after the manner of a varnish. 
Iris. — The alteration of the iris is manifest at all periods of the 
disease. The first and most important lesion is the loss of that 
contractile power which distinguishes this membrane. In the 
worst part of the disease its tissue appears to be swelled and tume- 
fied. It is then friable and easily crushed, and a very slight degree 
of pressure is sufficient to transform it into a soft black mass. 
The varnish spread over the posterior face, and which constitutes 
the uvea, has acquired a certain degree of viscosity and an adhe- 
sive property which causes it to adhere to the anterior portion of 
the crystalline. In process of time the turgescence of the iris dis- 
appears — its tissue decays and becomes dissolved in the aqueous 
fluid — the process of disorganization commences in those parts 
nearest to the small circumference, and gradually progresses towards 
the great concentrical ring of the iris, which becomes the limit of 
the pupillary opening before which the crystalline appears in 
relief. 
In many eyes affected with blindness black specks about the 
size of the head of a pin are perceptible, the last remaining vestige 
of a membrane which no longer exist : they are isolated, and dis- 
persed at intervals over the anterior plain of the lenticular body, 
with which they have contracted a close adherence. 
Crystalline lens. — An alteration in the position of this body 
takes place, which obliterates the anterior cavity, and pushes the 
iris into the interior of it. The crystalline capsule becomes 
opaque, parchment like, and cracked. The substance which it 
contains is softer and more pulpy than in a natural healthy state. 
In some cases it is actually in a state of deliquescence , and it is said 
that its constituent molecules have lost their affinity. 
The vitreous humour. — In a physiological state it is enclosed in 
a thin transparent pellicle, which throws out cellular prolongations 
communicating with each other. This anatomical disposition is 
completely subverted, the hyaloid membrane has disappeared, 
the vitreous humour has escaped into the globe of the eye, and, 
instead of being transparent, and of somewhat the same consistence 
as jelly, it is thick and partially liquefied. It has undergone an 
alteration analogous to that of the fluid in the anterior chamber, 
and has acted in a similar manner on the surrounding tissues. 
