340 RESEARCHES INTO THE CAUSES OF BLINDNESS. 
Part 1. Chapter I. 
The Morbid Lesions. 
In the essays that we have met with in the “Recueil de 
Medecine Veterinaire,” we have remarked that authors generally 
omit to state what were the morbid lesions observable in eyes 
affected with blindness, and the characteristics presented by them 
while in this state, and during the life of the animal. It appears, 
however, that these points are well worthy of consideration, since 
through them alone we are able to trace the modifications that 
take place in the interior of the eyes. It is only by adding 
together the observations made, or the alterations undergone by 
the external parts of the eye, and those resulting from careful 
dissection, that we can obtain any really useful data as to the 
nature, progress, and duration of these affections, or the period that 
elapses before they reach their fatal termination. We shall com- 
mence by calling in the aid of pathological anatomy, and then 
proceed to notice the various diseases which occasion blindness. 
These we have progressively followed out, and thus come to a 
consideration of the external influences which usually develope 
them. 
When examining animals blind in one or both eyes, it is re- 
marked that the same alterations of structure are not seen in all. 
In fact, two distinct divisions might be made, based on the dif- 
ference that attends the development and progress of the disease. 
In one the eye preserves its natural form, and all the accessory 
parts their integrity. The transparent cornea is sometimes opaque, 
and sometimes retains its natural transparency. The pupillary 
opening is considerably enlarged in consequence of the destruction 
of the circumference of the iris. The crystalline lens is of a dull 
white hue, and projects slightly into the anterior chamber. 
All atrophied eyes may be classed in the other, whether the 
conjunctiva and the eyelids are altered or not. 
If the eyes which we have classed under the first division are 
submitted to dissection, the following lesions will be discovered : 
— The transparent cornea is always thickened, and sometimes to 
twice or thrice its natural thickness. When in this morbid state, 
it is easy to perceive that it is composed of a superposition of 
layers united together by a highly serrated luminous tissue. 
These layers are not, however, so numerous as some anatomists 
have supposed. We have never been able to detect more than 
five or six ; they are opaque, and, in general, tolerably firm; the 
superficial layers not being so hard as the under ones. The same 
