699 
THE VETERINARY ART IN INDIA. 
By J. Grellier, Esq., M.R.C.S. 
[Continued from p. 651.] 
Inflammation of the Eye. 
The organs of vision are more subject to be diseased from 
natural causes than any other in the animal economy, which l 
imagine may proceed from the eye-ball being so compound in 
its structure ; its membranes and humerus so delicate, both in 
their texture and functions ; its vessels so minute, that the least 
irregularity in its circulation, whether from internal or external 
causes, must unavoidably produce obstructions or pressure on 
some of its parts, and any one part being defective destroys or 
deranges the mechanism of the whole. 
A minute description of the eye must tend rather to confuse 
than elucidate the subject ; and yet, that the reader should have 
some general knowledge of its structure and economy, I think 
requisite towards attaining a knowledge of its diseases. 
The eye is composed of several coats, containing humours for 
the purpose of refracting the rays of light and converging them 
to a focal point ; which point falls on the expansion of the optic 
nerve, seated on the posterior part of the eye, by w'hich the sense' 
of vision is conveyed immediately to the brain. 
This mechanical structure is founded on the first laws of optics ; 
consequently any person the least versed in that science may 
attain an immediate knowledge of the economy of the eye. 
It is divided into two chambers, the anterior, which contains 
the aqueous or watery humour, and the posterior, containing the 
crystalline or glassy humour. The rays of light, not being suf- 
ficiently refracted by the atmosphere, pass through the external 
coats of the eye, which, being convex, increase the refraction ; 
they then pass through the watery humour, which not only in- 
creases the refraction, but, perhaps, serves to keep a proper space 
between the refracting mediums : the rays not yet being suffi- 
ciently converged, pass through the crystalline lens, which, being 
hardest in the centre, draws the rays rapidly to a focal point, 
which is received on the expansion of the optic nerve, where the 
object is delineated, and is conveyed from thence to the brain # . 
* As the too great concavity or convexity of the eye is known to affect 
the human vision by removing the focal point from the optic nerve, may 
not the same causes produce that shyness on the road, and other symp- 
toms of imperfect vision in the horse, when the eye is perfectly free from 
disease ? 
