RESEARCHES INTO THE CAUSES OF BLINDNESS. 347 
comes on ; the horse is weak, and falls away rapidly ; and at 
length the lucid cornea bursts, as if to terminate this dreadful state 
of suffering. A quantity of albumino-purulent matter is dis- 
charged through the opening, floating in which are black and grey 
particles — the decomposed remains of an organ that no longer 
exists. Gradually the wound scars over, and the eye contracts 
and is drawn back into the orbital cavit}'. 
We have already stated our opinion that the inflammation in- 
ducing hydro-ophthalmia usually results from ill-treatment, and 
especially when the animal is out of health. Periodical ophthalmia 
is, as we have before stated, rarely met with, at least if by this 
we understand a disease having three distinct phases, during which 
there is successively the formation and re-absorption of morbid 
products, and a return of the eye to its habitual and natural state. 
It is true that in some cases we have noticed a very considerable 
diminution of the ophthalmic symptoms; but the pathological 
deposit which takes place in one of the portions of the anterior 
chamber is neither in form nor colour similar to that which appears 
in the second epoch of periodical ophthalmia ; in the cases also of 
which we are treating the symptoms do not entirely disappear ; 
the eye squints a little, there is a peculiarity in the pupil and 
the iris ; and, not unfrequently, it re-appears with every symptom 
aggravated, but still differing widely from periodical ophthalmia. It 
must, however, be admitted that all diseases of the eye have a kind of 
family likeness, so that we are in doubt whether the same causes 
might not produce them. Guided by this persuasion, we shall, in 
the next chapter, treat of our etiology, and trust that our researches 
may assist in clearing up this most obscure point of veterinary 
pathology. 
Before setting to work, we must point out the chief chasms in 
our treatise, and which we trust to see filled up by some of our 
brethren who are led to devote their attention to this study. 
Having regarded our subject more in a hygienial than in a patho- 
logical point of view, we have omitted to ascertain the date of the 
lesions of the eye, and the succession of morbid action which has 
operated before it was brought to the state which we have described; 
but trust that some veterinary surgeons resident in the neighbour- 
hood, and who have it in their power to follow the horse from 
year to year, will supply this deficiency. 
The same remark applies to the treatment, which they, better than 
many others, are enabled to demonstrate ; viz. whether in some 
cases it is not possible to diminish a portion at least of the fatal 
effects of the causes we are about to enumerate. 
