346 RESEARCHES INTO THE CAUSES OF BLINDNESS. 
At some distant time we hope to demonstrate that the brutality 
of carters and drivers has much to do with the development of 
internal ophthalmia. 
We return to the usual course of this affection, the progress of 
which is generally slow. It continues its ravages in the interior 
of the eye, while the anterior surface assumes a yellow or earthy 
hue. The edges of the pupil dilate, and the crystalline, already 
dull and opaque, projects into the anterior chamber. Sometimes, 
however, it happens that all these morbid characteristics are hidden 
from view, in consequence of the continuance of the opacity of the 
lucid cornea. At this period, that is to say, about two months 
after the first appearance of the disease, those alterations commence 
of which we have already spoken under the head of morbid lesions. 
Second variety . — It is exceedingly difficult to enter into the 
examination of this. Its progress is insidious ; the symptoms 
are but obscurely developed, and the chief seat of evil is in the 
internal parts of the eye. To these obstacles are added, the dif- 
ficulty experienced by the veterinary surgeon in obtaining any 
thing like a satisfactory examination of his patient, while he is kept 
constantly at hard labour, and, unless the locomotive organs them- 
selves are affected, little time is allowed. 
At this period the animal is ever on the qui vive, because he 
perceives nothing clearly, and all objects are confused and indis- 
tinct. Nothing suffices to terrify him and cause him to start and 
close his eyelid. The eye no longer retains that brilliancy which is 
characteristic of its physiological state, but it is very sensible of 
light, and reflects from the base a hue varying between pale yellow, 
dirty grey, and green. As the disease progresses, and the functions 
of the eye become impaired, the pupillar opening materially 
contracts ; the crystalline lens diminishes in size, doubtless in con- 
sequence of the destruction of the hyaloid membrane, and the 
absorption and coagulation of the humour which it contains. 
In general, this ophthalmia reaches its fatal termination without 
presenting any other symptoms than those which we have narrated. 
So slow and obscure is its progress, that we not unfrequently 
see horses become blind in one or both eyes without having 
betrayed any inflammation of the conjunctiva; while, on the 
other hand, the attendant paroxysms are most intense in some 
cases ; the eyes cloud rapidly over, become exceedingly suscepti- 
ble of light, and are almost constantly veiled by their lids. 
Aqueous humour is abundantly secreted, the lucid cornea becomes 
perfectly opaque, and its superficial layers begin to soften. After 
two or three days of suffering, the eyes increase in bulk, and be- 
come so prominent as to produce tension of the lids. The agony 
of the animal has then reached its height; the fever of reaction 
