60 



their moist clay soils, to the development of the microbe, 

 the parasite, the gas or miasmatic factor that causes this 

 disease. Records also show that on certain low lands of 

 Belgium, France, Spain, Italy. Austria and England, this 

 eye disease prevails extensively. Likewise in our own 

 country certain localities have more cases of moonblindness 

 thau others. 



The writer has observed that this disease is more prevalent 

 in the southern states, than in the central or northwestern 

 states. Compare the number of cases in the dry, cool climate 

 of South Dakota with the moist, Avarm climate of Alabama 

 and the result shows the extremes — ^the almost complete ab- 

 sence in the former State and the unpleasant prevalence in 

 the latter. It is said to occur less frequenly on lime soils. 

 Clay soils will retain moisture longer and as a rule are richer 

 in organic materials than sandy soils; consequenly germs, 

 malarial parasites, etc., will grow abundantly on the moist 

 clay soil. 



The disease appears on sandy soil if there is sufficient 

 moisture; it will also appear on moderately high rolling 

 land irrespective of the kind of soil if there be sufficient 

 moisture — as a rainy season followed by a warm season with 

 occasional heavy rains. A number of cases have been ob- 

 served at Auburn, 800 feet above the sea level, with a gray 

 sandy soil; however, there are red clay districts not far from 

 Auburn. I, also, have reports of its appearance on sandy 

 soils in other parts of this state. 



In the period from 1879 to 1890, appeared 2183 cases of pe- 

 riodic opthalmia among the horses of the Prussian army. Of 

 this number 585 were in the 15th army corps; 358 in the 

 first; 339 in the 11th; 145 in the 10th; 135 in the 5th; 

 about 80 in the 2nd, the third and the 8th; about 70 in the 

 7th ; about 60 in the 4th, the 6th, the 9th and the 14th ; 49 

 in the guard corps. It will be observed from the above re- 

 cords that the disease prevailed quite extensively in the 



