RESEARCHES INTO THE CAUSES OF BLINDNESS. 341 
peculiarity is observable in the whitish matter that lies in the cel- 
lular tissue separating the succession of layers, and almost form- 
ing new ones somewhat thinner than those composing the trans- 
parent cornea. This matter found between the layers, is it the 
produce of an inflammation similar to that observable in other 
organs of the frame 1 We think not, but are rather inclined to 
regard it as the aqueous humour altered, and modified, and changed 
in its nature and mode of secretion, and which has caused the 
opacity and thickening of the cornea. Nor is this opinion the 
mere expression of a theoretical notion, but a fact founded on an 
attentive examination of the aqueous humour, and a comparison 
of it with the matter situated between the layers of the cornea. 
If this fluid is poured on a plate, it will be seen that it is clouded, 
thicker than in its natural state, and that it holds in suspension a 
number of minute white specks. On dissecting the anterior 
chamber of the eye, a thin layer will be found — a species of jelly — 
similar to that which exists among the layers of the cornea, and 
this analogy becomes peculiarly striking when we examine this 
substance in those parts of the cornea that are nearest to the 
anterior chamber. The only difference of any note is, that of the 
density not being so great. In two cases, on raising the layers 
one after another we have found an uncongealed liquid precisely 
similar to that contained in the anterior chamber of the eye. 
These anatomico-pathological considerations of the cornea lead 
us to speak of its opacity. This morbid phenomenon in cases of 
internal ophthalmia has not yet, so far as we are aware, received 
any satisfactory explanation. 
In our dissections we have frequently remarked that the opacity 
was more decidedly pronounced in the interior layers than in those 
situated at a greater distance from the aqueous humour. This 
fact may be verified by examining the profile of the horse. In 
by far the greater part of those which we have seen, the superficial 
parts of this membrane were transparent, while the inferior parts had 
lost their lucidity. These two characters, united with the morbid 
lesions, confirm our suspicions that the opacity proceeds from the 
back-ground forwards, and from the interior towards the surface. 
In such case morbid phenomena, far from being a primitive effect 
direct from the disease, are but secondary and purely physical 
action produced by the imbibing of the altered aqueous humour. 
When speaking of internal ophthalmia, we shall enter more fully 
into this subject. All these researches are made with difficulty, 
and require great patience and perseverance ; and it is also right, 
that the persons making them should have the opportunity of 
examining a great number of diseased eyes, for carelessness or 
unskilfulness frequently nullify the whole dissection. 
VOL. XVIII. 3 A 
