PERIODIC OPHTHALMIA. 89 



tliat doubt about the nature of the case be prolonged even be- 

 yond the first attack, the supervention of another similar paroxysm 

 will settle the point at once. 



Geldings more subject than Mares to Ophthalmia. — 

 Of the fifty cases of troop horses recorded in my own practice, 

 thirty-nine have occurred in geldings, eleven only in mares. How 

 is this] D'Arboval, who has chronicled the same fact, accounts 

 for it on the supposition that there is a connection between dentism 

 and ophthalmia. He thinks that the greater irritation occasioned 

 by the cutting of the tusks than of the other teeth, renders geldings 

 more subject to the disease. That, so far as irritation is concerned, 

 constitutional even as well as local, the tusks produce more in the 

 course of their eruption than all the other teeth together, I can 

 readily testify ; and therefore, if it can be proved — as will be seen 

 when we come to the etiology of the disease — that dentism is a 

 cause of ophthalmia, the reason of the special liability of geldings 

 becomes evident. 



The Eye most disposed to the Disease, according to my 

 own observation, is the small dark-looking one, that which by no 

 chance whatever is seen to disclose any appearance of white. 

 Every body appears to view wall-eyes as all but exempt from 

 ophthalmia. I have not had much to do with wall-eyes myself, 

 and therefore can hardly speak concerning them : but Mr. Castley 

 " remembers two horses in particular, officers' chargers, whose eyes 

 were of that description which is said never to go blind, but which 

 became affected under exactly similar circumstances : one had 

 brown or hazel-coloured eyes like that of a sheep, the other was a 

 wall-eyed horse; and they were seven or eight years old." Dis- 

 ease in their eyes supervened on states of debility, consequent on 

 repeated attacks of diabetes, or v^iihex polyuria. I am informed by 

 Mr. Goodwin — the Queen's Veterinary Surgeon — that, so far as 

 the eyes of cream-coloured (Hanoverian) horses are concerned, he 

 has never observed any thing peculiar in their diseases. 



The Causes of Periodic Ophthalmia demand the greatest 

 attention from us, both on account of the light Avhich they shed 

 upon the nature of the disease, and of the suggestions they furnish 

 us with for its prevention. 



VOL III. N 



