PERIODIC OPIITIIALIMIA 95 



as were relapses, we shall find the proportion still greater. Added 

 to which, these horses of officers may be regarded, most of them, 

 as seasoned subjects — horses who have passed unscathed through 

 the hot atmosphere of the stable, and have now become inured to 

 it. It is not likely that the officers purchase any horses having 

 diseased eyes : the veterinary surgeon, to whom they are com- 

 monly shewn, takes care to prevent that. So that I really do not 

 see that this fact — for fact and truth it is — operates against the 

 doctrine of our late Professor. 



A Regiment of Cavalry, although it affords no very large 

 field of observation, yet, under watchful and observant eyes, fur- 

 nishes facts of a nature that may, to the extent of their bearing, 

 be safely reasoned upon. Strings of horses come from the breeders, 

 through dealers' hands, into regiments ; and these horses, prior to 

 admission, are all of them carefully and closely examined by vete- 

 rinary surgeons; by whom any of them that had defective eyes, or 

 exhibited any signs even denoting they had been the subjects of 

 periodic ophthalmia, would most assuredly be refused. It is there- 

 fore fair to conclude that, so far as appearances go, they all enter 

 the service with perfectly sound and healthy eyes. And I may add, 

 it is very rare indeed to have occasion to reject one on account of 

 the eyes. In fact, what disease they get in their eyes they con- 

 tract after they come under the observation of the veterinary sur- 

 geon. Nor can we deny that there present themselves, in the course 

 of their domestication, causes both for general and local plethora ; 

 or that there are times when the stables in which they stand, 

 many of them together, separated only by bails, must be hot and 

 impure too, notwithstanding the precautions taken to ventilate them. 



To WHAT, THEN, IS THE OPHTHA.LMIA TO BE ATTRIBUTED ? 

 The advocate for hereditary influence answers, "to the circumstance 

 of the parents having had it;" while others say, ''No!" but to 

 *' nervous influence," to "plethora," to "heat," to "a contaminated 

 atmosphere." — For my own part, however much hereditariness or 

 other causes may predisjyose the animal to take the disease, I 

 cannot help thinking — and I am led to think so by observation and 

 experience — that many horses who now contract ophthalmia in 



