Hereditary Diseases of Horses. 



119 



titles of periodic, specific, or constitutional ophthalmia and moon- 

 blindness. In this disease the inflammation involves, to a 

 greater or less degree, all the internal parts of the eye, exhiliits 

 a great tendency to effusion of lymph, often attacks only one eye 

 at a time, but, on subsiding in the one first affected, is very apt 

 to appear in the other ; always leaves the eye affected dim, 

 weak, and susceptible to a future attack, and is seldom entirely 

 got rid of until blindness of at least one eye has been induced. 

 The symptoms of this disease are usually tolerably well marked. 

 The mucous membrane and its various appendages are inflamed ; 

 there is copious secretion of tears, great pain and tenderness, and 

 marked intolerance of light. The cornea becomes opaque and 

 for some time intercepts the view of the parts within. The eye- 

 lids are nearly closed, and the eye-ball within when visible 

 through the cornea soon loses its clear transparency, in conse- 

 quence of the humours becoming of a muddy yellowish-brown 

 colour from effusion of lymph. Febrile symptoms are present, 

 and are greatly more intense than might be anticipated from 

 the comparatively small size of the part affected. After two 

 or three days there is often a remission in the intensity of the 

 disease, the external parts being less inflamed and the dull 

 muddiness of the cornea and interior gradually diminishing. 

 A recurrence of the acute inflammation, or its ti'ansference 

 to the previously sound eye, is always, however, much to be 

 dreaded. Sometimes the eye apparently recovers, and the 

 superficial observer might consider it perfectly healthy, but the 

 more experienced will find, on careful inspection, sufficient 

 e\ddence that the organ has been the seat of disease, and that 

 there still remains a change of structure which predisposes to 

 subsequent attacks. The eye seems smaller than its fellow, and 

 still remains intolerant of light ; the cornea is often dull, the 

 margins of the pupil frequently uneven and ragged, arid the 

 movements of the iris impeded by adhesions ; the more deep- 

 seated parts have a peculiar leaden appearance, and shreds of 

 IjTnph may sometimes be observed floating in the aqueous 

 humor, or embedded in the crystalline lens or its capsule : the 

 last condition constituting what is technically called a cataract. 

 This may vary much in size, being sometimes a speck scarcely 

 perceptible, and interfering slightly with vision ; at other times 

 large, with white lines passing outwards in every direction, and 

 causing nearly total blindness. Eyes having any of these 

 appearances must be regarded as unsound, and specially suscep- 

 tible of inflammation, which is apt to be excited in them by such 

 causes, as exposure to cold, high feeding, over-work, or debility, 

 •and is liable to return again and again, until the animal is totally 

 blind. But before the occurrence of an acute attack it is scarcely 



