Recurrent Ophthalmia in Solipeds. Moonblindness. 411 



2. Its appearance in certain predisposed systems, whenever an 

 injnr)'^ or debilit}' of the eye seems to open the way for the ad- 

 mission of the hypothetical microbe. 



3. The increased susceptibility to the malady when the system 

 has been debilitated by disease, overwork, heating food, bad hy- 

 giene, or parasitisms, which have undermined the native power 

 of resistance. 



4. The prevalence of the affection in given localities has been 

 supposed to imply the preservation and perhaps the multiplica- 

 tion of the germ in such places. 



5. The increasing number of victims, year b\- year, when the 

 same regiment or stud has been kept for a number of years in the 

 same place. The theory is that with the presence of infected 

 horses the hj'^pothetical microbes become increasingly prevalent 

 in the locality and above all in the stables, until even the more 

 resistent subjects tend to succumb under the repeated infections. 

 Thus Zundel says that in 1878, 700 army horses were stationed in 

 Saarsburg, in 1879, 6 were attacked with recurrent ophthalmia, 

 and in 1880, 84, Hofgeismar mentions that a dragoon regiment in 

 Frankfort had 5 horses attacked in 1876, 12 in 1877, 11 in 1878, 

 14 in 1879, and 42 in 1880. We have, however, no assurance 

 that the excessive rainfall, spoiled food or other unhygienic condi- 

 tion, may not have been a potent factor in the increase. 



6. The obvious connection of certain cases of recurrent oph- 

 thalmia with a rheumatic condition suggests the probable opera- 

 tion of the same microbian cause. 



Up to the present the microbian causation of this malady cannot 

 be taken as proved, yet as a hypothesis it explains satisfactorily 

 many of the observed morbid phenomena. That there is no such 

 rapidly spreading infection, as would warrant us in listing this 

 with animal plagues, is conceded, and that constitutional condi- 

 tions have a potent influence is allowed, but that, in addition to 

 these, microbian invasion is often a means of precipitating the 

 malady is altogether probable. It may not be necessary that the 

 microbe should in every case be of the same kind, yet the addi- 

 tion of a germ as the last item in the chain of causes is presump- 

 tively true. 



Parasitism. Willach claims that many cases are directly due 

 to parasites in the eye. In 19 affected eyes he found one young 



