58 



sight ; thereafter that eye remains free from periodic inflam- 

 matory attacks; the other eye is then liable to become simi- 

 larly affected until it goes blind. Rarely are both eyes thus 

 diseased at the same time, but they may be attacked alter- 

 nately until each one becomes blind. 



The diagnosis of periodic opthalmia is not difficult. The 

 previously mentioned symptoms and course of the disease 

 are generally quite distinct. There are exceptional condi- 

 tions and times when the owner or observer will be in doubt. 

 During the first attack, when the cornea and the aqueous 

 humor are so badly clouded that the pupil, the iris and all 

 internal parts of the eye are invisible, one can not determine 

 beyond question whether it is a case of simple iritis or iritis 

 associated with some form of influenza. In some attacks 

 the cornea may be so opaque for a time that one is unable 

 to discover whether the aqueous humor is clouded or not; 

 in such a case the owner may believe that the cornea is in- 

 jured in some way. Time alone will bring forth or make 

 clear the other symptoms. Again, during the interval be- 

 tween the first and second or between the second and third 

 attacks, the before mentioned symptoms may be indistinctly 

 marked; it will then be necessary to wait for the appearance 

 of another attack. But in all the doubtful, indistinct cases, 

 the characteristic fact of its recurrence in the same eye will 

 remove all doubts in the mind of the owner if not in the 

 mind of the buyer. 



Causes. — A number of different microbes have been found 

 in the tissues and humors of eyes affected with moon blind- 

 ness. Vigezzi has found a micrococcus which he believes 

 to be the direct cause of the disease ; Trinchera discovered 

 an immovable, curved bacillus ; E. Koch found a short bacil- 

 lus, rounded at its ends; Richter found a diplococcus and a 

 triplococcus. However, no positive proofs have as yet been 

 discovered, by experimentation or otherwise, that would jus- 

 tify a positive declaration in favor of any microbe. In fact 



