VETERINARY OPHTHALMOLOGY. 99 



sympathetic ophthalmia. So, if the eye be injured to 

 -a grave degree, enucleation is tlie word. 



Irido-choroiditis^ Periodic Opldhahnia^ Jflecciirrent 

 Ophthahnia., Moon hlindness^ {Irido-cyditis). — This 

 iiffection is intimately related to certain climates; 

 systems and soils, and shows a strong tendency to re- 

 cur again and again. Usually terminates in blindness 

 from cataract. Its causes may be said to be, primarily, 

 in the soil — on frequently submerged groiinds ; on 

 marshy and clayey grounds ; on coasts. Also wet, 

 damp climates, which produce lymphatic constitutions. 

 Again, rank, watery foods. This affection is usually 

 seen during the dentition and breaking period ; there- 

 fore are apt to see it between two and five or six. 

 Among local causes would be smoke, acrid vapors, dust, 

 etc. No one of these is sufficient to cause this disease. 

 To-day a microbe is the alleged cause, or the product 

 of a microbe. This product may be preserved in the 

 marshy soil. The presence of a definite germ has not 

 "been demonstrated as yet. 



Heredity is one of the most potent causes we know. 

 This is very positively demonstrated when both 

 parents have suffered. In support of this, w^e know if 

 a mare had borne a number of foals, all sound, and 

 then suft'ered an attack of periodic ophthalmia, the 

 subsequently born would also suffer. The study of 

 atavism presents many interesting facts in these 

 PAPitt^r'i. An''] yet if *,be foals of diseased parents be 



