462 THE DISEASES AND DISOEDERS OF THE OX. 



flukes. Moisture being an essential for the development of the 

 fluke, it is best to keep sheep on dry and well-drained ground, 

 and low-lying farms especially should be thoroughly drained. 

 Sheep which are folded are perhaps less frequently attacked than 

 those at pasture, turnips not being so likely to harbour cercariae. 

 Sheep should be kept from stagnant ponds. Salines and 

 especially common salt are highly beneficial by way of treat- 

 ment. On no account whatsoever should the flesh of sheep in 

 the final stage of sheep-rot be eaten. 



Sheep-rot generally breaks out in districts where the soil and 

 sub-soil are of a clayey nature, and where consequently there is 

 little or no natural drainage. On the contrary, the disease is 

 rare or absent in sandy, gravelly, or calcareous districts. The 

 character of the soil seems to be of the first importance ; for, 

 according to Thomas, all fields upon the Oxford clay have been 

 dangerous, whether exposed to floods or not, whereas floods on 

 low porous grounds, or on gravel, appear to be innocuous in 

 regard to sheep-rot, unless the water has remained stagnant for 

 a long time. 



After a very wet summer, rot is prevalent, water being neces- 

 sary (together with a certain degree of warmth) for the growth 

 of the larval fluke. If, however, floods occur, land which is 

 badly drained and liable in ordinary seasons to develop rot in 

 the sheep placed upon it, may become a veritable swamp, and 

 consequently free from rot, since the cercariae cannot become 

 encysted where there is much water. On the other hand, 

 land which is under ordinary circumstances well drained, and 

 has been free from rot for years, may be a prolific source of the 

 disease in very wet seasons. Ruminants are especially subject 

 to rot, since the encysted cercariae can remain in them without 

 being destroyed for a long time in the first, second, and third, 

 stomachs, whose secretions are not digestive. Further, sheep 

 are especially liable to it, because they can graze so closely, 

 closer in fact than any other quadruped except the kangaroo. 

 The cysts become attached to stalks of grass near the damp 

 roots, and hog-faced sheep which cannot crop close to the 

 ground do not swallow the cysts, and hence do not become 

 rotten. Again, lambs at Michaelmas graze more closely than 

 ewes do, and are consequently more subject to rot than full- 

 grown ewes and wethers. Salt kills the liver-fluke in every 



