208 DISEASES OF SHEEP. 



The following questions will naturally occur to many 

 of my readers. What gives rise to these tubercles ? 

 what are the predisposing causes which lead to their 

 formation? and, when formed, how do these appar- 

 ently unirritating bodies produce effects so baneful? 

 Queries like these, however, cannot shortly be replied 

 to, leading, as they do, to discussions which embrace 

 many curious theories ; but as the negative mode of 

 teaching is often of avail where the positive or more 

 direct would fail to bring conviction, I shall, before 

 proceeding to allude to what the causes are, endeavour 

 to state what they are not. 



Imaginary Causes of Rot. The liver-fluke has long 

 been looked upon as the origin of rot, and this opinion 

 has now become so deeply rooted, and taken so fast a 

 hold of the public mind, that if I were to contradict it 

 by plain assertion, I should only be striving to buffet 

 singly a tide of opposition. The best way, therefore, 

 will be to examine a few of the theories supposed to be 

 confirmatory of the notion that fluke worms are the 

 beginning of the mischief, and then see whether their 

 supporters have managed to make good the point. 



I. The fluke is supposed to get into the liver of the 

 sheep by being swallowed, and this, according to our 

 theorists, may be brought about in some of the follow- 

 ing ways : - 



1. The eggs may be floating in the air, and thus 

 accidentally reach their destination. This is the view 

 taken by the celebrated Clater ; but if he had been, in 

 this instance, a man of experiment, rather than of idle 

 conjecture, he would have found, as any one readily 



