306 THE DISEASES OF SHEEP. 



countless numbers, often lodging on the grass. If they 

 fall on dry soil, they are harmless; if on wet soil, the 

 disease is propagated to other sheep. The egg is oval in 

 shape, has a lid at one extremity, and contains an em- 

 bryo which, when matured, is provided with delicate, 

 hair-like processes known as cilia. The lid is lifted, al- 

 lowing the embryo to escape. The latter at once begins 

 to search for a particular snail (the Limnus truncatulus), 

 whose body it penetrates by the aid of a boring appara- 

 tus. It undergoes a series of wonderful changes in form, 

 passing through several generations, until a tadpole-like 

 creature is produced. Emerging, it encysts itself in the 

 lower part of the blades of grass, from whence sheep pick 

 it up in grazing. 



Sheep are more susceptible to rot than other animals 

 simply because they bite closer. A hog-mouthed sheep 

 escapes; but many cattle and sometimes, in wet seasons, 

 colts also suffer. 



Rot is never seen on dry lands, nor on salt marshes; 

 and even rotting grounds are safe after a frost. 



Prevention. — Drain, and thereby kill the snails; salt 

 the 'pastures, and thereby kill both the snails and embryo 

 worms; slaughter sheep, mixing their excrements with 

 lime or salt; destroy the liver, intestines, &c, totally. 

 Isolate sound sheep. 



The disease can be detected early by the sheep thriv- 

 ing very rapidly and by the yellow tinge of the membrane 

 of the eye. 



Remedy. — Concentrated, dry food. Common salt and 

 ferrous sulphate dissolved in water, given daily, mixed 

 with bran or crushed grain. Slaughter all marketable 

 sheep. 



For doses of ' furrous sulphate' (sulphate of iron), see 

 page 21. 



