574 Veterinary Medicine. 



By 1895 it prevailed over an area of 300 square miles. It made 

 its advent in 1891 in four or five large flocks (2,000 to 10,000 

 head each) on land which they had occupied for nine years, and 

 so disastrously that several sheep ranchers, after an experience 

 of a year or two, sold out to the butcher and abandoned the 

 sheep industry. 



All or nearly all cases seen in 1896 were in parturient ewes, 

 (4 to 6 days after parturition), the constitutional condition attend- 

 ing on lambing proving a most potent factor in causation. 



The protozoon repeated the characters of that found in the 

 sick sheep in Italy and the Danubiau delta, and the conditions of 

 the blood and the structural lesions supported the idea of identity. 



Altitude seems to have little or no effect as a causative factor, 

 as the disease is domiciled alike on the low alluvium of the 

 Danube and the Deer L,odge Valley of Montana over 5,000 feet 

 above the ocean. In both regions there is the common condition 

 of inundation or its equivalent irrigation, for the Montana range 

 is dry and arid, interspersed with alkaline bogs inimical to vege- 

 tation, but prolific and fruitful under irrigation. The Montana 

 disease has been attributed to mineral poisons carried on the 

 winds from the extensive copper smelters in Butte and Anaconda, 

 but the smelters had been in existence for eight or ten years be- 

 fore this disease was observed, and from its appearance the infec- 

 tion has gradually extended, attacking sheep only, and sparing 

 other domestic animals, which would have suffered as well 

 from a mere mineral poison on the vegetation. The doctrine 

 of a mineral poison is equally contradicted by the habitual preva- 

 lence of the disease in spring and autumn, while it is dormant 

 in winter and summer. In winter the flocks eat hay cut from 

 the richer valley lands and meadows, while in summer they are 

 pastured on the foothills and mountains, and drink from the 

 mountain springs surrounded by alkaline bogs. The autumn 

 outbreak occurs long after the mountain grasses have dried up, 

 when the flocks are thrown back on the supplies obtained from 

 the alkaline bogs and the valley pastures. In late winter and 

 early spring the growth naturally starts first in the same boggy 

 and valley areas, and both facts suggest a microbian infection — 

 protozoan or bacteridian. If an intermediate host or bearer — in- 

 sect or other invertebrate — is to be assumed it implies two gen- 



