Verminous Bronchitis and Pneumonia in Sheep. 377 



and some observers have inferred that the latter take years to 

 reach maturity. The difference may, however, be otherwise ex- 

 plained, the rufescens, living in the air sacs and cells, causing 

 greater destructive changes in the lungs and thereby killing off 

 the lambs at an early stage, while the more robust mature sheep, 

 can survive the first attack, and thus go on taking in a new 

 stock of the young wornjs at intervals. 



History of the Disease. The malady was first described by 

 Daubenton in 1768, as being very destructive at Montbard, 

 France. Since then it has been recognized in nearly all parts of 

 the world and in many cases its introduction into a new district 

 can be traced by the importation of infested sheep. It prevails 

 extensively all over Europe, and is mo.st destructive in the southern 

 and midland counties of England and in New South Wales. It 

 is common in New York, and Connecticut, and in many parts of 

 Illinois, and years ago on the unfenced prairies of Iowa it threat- 

 ened the destruction of the sheep industry. 



Conditions Favoring the Disease. The essential cause of 

 the malady is the. parasite , but that being present, many conditions 

 favor its encrease and diffusion and the receptivity of the sheep 

 on infested pastures. 



Wet Seasons. As in the case of worms generally, the abun- 

 dance of water favors the preservation of the embryo, and its 

 moulting which fits it for a new internal habitat. 



Marshes, pools, lakes, ponds, streams, rivers, damp bottom lands, 

 natural basins, inundated lands, deltas, low islands, fens, damp 

 springy ground, and irrigated pastures are especially favorable to 

 the preservation of the worm, and hence its frequency in Holland, 

 Belgium, the English fens, and in all low damp lands that have 

 once become infested. 



Watershed. The embryo worm is easily carried in streams 

 hence the access of sheep to water that has drained from infested 

 pastures at a higher level is a fertile source of the malady. 



Dry Seasons. While water is essential to the preservation and 

 moulting of the embryo, yet a drought following such moulting 

 may preserve the larva indefinitely by drying it up, and arresting 

 vital changes without destroying its vitality. Thus an excess of 

 moisture and a drought may successively contribute to the preser- 

 vation, and diffusion of the strongyle. 



