THE DISEASES OF SHEEP 333 



peratures below 40 F., as already stated, the eggs 

 remain dormant. 



METHODS OF PKEVENTING INFECTION. 



It is evident from the foregoing statements that 

 in the northern part of the United States, under 

 usual climatic conditions, infested and non-infested 

 sheep may be placed together in clean fields the last 

 of October or first of November and kept there until 

 March or even later, according to the weather, with 

 little or no danger of the non-infested sheep be- 

 coming infected. If moved then to another clean 

 field they may remain there nearly the entire month 

 of April before there is danger of infection. From 

 the 1st of May on through the summer the pastures 

 become infectious much more quickly after infested 

 sheep are placed upon them, and during May it 

 would be necessary to move the sheep at the end of 

 every two weeks, in June at the end of every ten 

 days, and in July and August at the end of each 

 week, in order to prevent the non-infested sheep 

 from becoming infected from the worms present 

 in the rest of the flock. After the 1st of September 

 the period may again be lengthened. This method 

 of preventing infection in lambs would require a 

 considerable number of small pastures or subdivi 

 sions of large pastures, and in many instances could 

 not be profitably employed, but in cases where it 

 could be used it would undoubtedly prove very effec- 

 tive. By the time the next lamb crop appeared the 

 pastures used the year before would have re- 



