78 CAUSES OF UNSOUNDNESS. 



and the time usually occupied, by corresponding 

 ocular changes, in other animals. A blow over the 

 eye is Hable to produce cataract (concussion 

 cataract) immediately after the infliction of the 

 injury, hence the argument would be in favour 

 of the vendor. The same remark applies when 

 the eye-ball has been wounded (traumatic cataract). 

 But injury is not the commonest cause of this 

 disease, cataract being generally of slow develop- 

 ment, and very often found to be the result of 

 advanced age. Supposing that the disease was 

 present in a horse over eight or ten years old, the 

 chances are that it has been of gradual develop- 

 ment, and in existence at the time of the sale. 

 The existence, or non-existence of cataract in 

 the subject of litigation, is more hkely to arise 

 in argument, than that relating to its duration. 

 This matter can, however, only be settled 

 by expert evidence, ophthalmoscopic examination 

 being the thing most to be relied upon. A test 

 commonly employed for the purpose of detecting 

 cataract is that known as the catoptric, which 

 consists in taking the horse into a darkened stable 

 and examining the eyes with the aid of a lighted 

 candle. Three images of the flame are seen upon 

 the surface of the cornea, two of which are erect 



