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or third day, has a beneficial effect. In very severe cases, the 

 ulceration extends through the external coats, the humour then 

 escapes, and the eye is lost. 



633. Periodic Opthalmia. — This differs very much from simple 

 opthalmia, in attacking the internal structures of the eye, usually the 

 anterior chamber. Formerly, it was supposed to come on with the 

 changes of the moon, and got the name of moon blindness, whilst, on 

 account of its tendency to recur, the term periodic was used. It is 

 not so prevalent as it used to be, and when it does occur, town horses, 

 as a rule, are the sufferers. Its causes are not well understood, but 

 are generally considered to be of a constitutional character ; sudden 

 changes from heat to cold, bad ventilation, and defective drainage, 

 are also blamed. In my opinion, one great cause is through an injury 

 brought about by the horse throwing up its head, in a low-roofed 

 stable, and thus hitting itself behind the ears, or it may arise through 

 the infliction of a brutal blow from a stick in that region. Some 

 think it has a hereditary tendency; such, however, has not been my 

 experience. Symptoms. — As a rule, the attack is sudden, the horse is 

 very dull, hangs its head, and has one or both eyelids closed ; the 

 upper lid has a flat and wrinkled appearance, owing to the eye being 

 pulled back into its socket. The animal cannot bear the light, and, on 

 examining the e3'e, it is found to be dim, having lost its lustre, the 

 front chamber appearing of a yellowish amber, sometimes a reddish 

 brown colour, and the pupil can scarceh' be seen. Frequent attacks 

 implicate the crystalline lens, and finally end in cataract. 



634. Treatment. — Put the animal into a room)', well-ventilated, 

 but darkened loose box, keep it perfectly quiet, and administer mild 

 doses of laxative medicine, say two ounces epsom salts, and half 

 ounce cream of tartar, night and morning, in a mash of bran, or as a 

 draught, until the bowels show relaxation. The eye should be 

 sponged with a weak solution of extract of belladonna, two or three 

 times a day. This treatment, in some cases, may be all that is 

 required ; but in protracted cases, I have found great benefit arise 

 from the application of a blister on the side of the cheek, or behind 



