406 RESEARCHES INTO THE CAUSES OF BLINDNESS. 
we can hope to throw any light on a question that has hitherto 
been enveloped in so much obscurity. 
They who attentively observe the horse will be surprised to find 
how often the commencement of ophthalmia coincides with the first 
symptoms of strangles, the precocious development of which is al- 
most always brought about by the animal having been prematurely 
worked, and exposed to neglect and ill treatment. 
In order to elucidate as much as possible a subject that is occa- 
sionally obscure, we will first attend to this fact, and, after having 
rapidly glanced at the modifications which locality produces on 
strangles, we will return to the chief subject of our attention, viz., 
ophthalmia. 
If it is true that diseases assume aspects varying with the kind 
or breed of animal, or with the climate, seasons, temperature, wor k, 
treatment, and food, the physiologist who wishes to establish this 
fact could not find a better example to illustrate his theory than 
STRANGLES. There is, in fact, no disease so variable, so susceptible 
of metamorphoses, and of taking on different forms, and appearing 
under different aspects. It is our intention, at some future day, to 
devote ourselves entirely to this subject, to point out the influence 
exercised by it on the welfare of animals. 
Horses are liable to strangles from two years and a half to four 
years and a half or five years. In most of them its appearance is 
unattended with any exaltation of the vital powers — all the functions 
of respiration, circulation, and digestion, continue calm and unaltered. 
A certain degree of langour while in repose, and heaviness when at 
work, indicate that the animal is unwell. Shortly after, the appe- 
tite flags — the pulse becomes low — the animal seems depressed — the 
eye is dull, and the conjunctiva pale and infiltrated — the pituitary 
gland is cold and injected — there is more or less discharge from 
both sides — a slight mucous rale is audible in the trachea — some- 
times there is no discharge from the nostrils, but a slow tumefaction 
in the parotidean region, accompanied by bad cough. This goes 
on for twenty or five-and-twenty days. No alteration takes place 
in the treatment of the animal : he is fed and worked as usual, and 
the drivers or carters contrive to awaken every flagging energy by 
repeated applications of the lash. 
In the course of this disease a species of ophthalmia is not un fre- 
quently seen, which is evidenced by injection of the conjunctiva, 
unaccompanied by redness or dulness of the cornea, and opacity of 
the aqueous humour. In the commencement there is a discharge 
of corroding tears, which shortly become purulent. At the expira- 
tion of three weeks or a month the animal is considerably better, 
especially if a seton has been inserted in the chest. This improve- 
ment is characterized by a diminution in the secretions, and by the 
