212 



DISEASES OF EHEEP. 



sion must at once be drawn, that as living flukes can- 

 not reach the liver from without, they must of a neces- 

 sity be produced only in particular states of the animal 

 they inhabit. How they originate we cannot of course 

 determine, and this is not the place to hazard physio- 

 logical conjectures ; but it will be found that their 

 appearance in the bile is always preceded by tubercu- 

 lous deposits in the lungs or liver. This I have proved 

 by numerous dissections, in which I have occasionally 

 found tubercles without flukes, but never met with 

 flukes where I did not at the same time discover 

 tubercles. Fluke worms, therefore, can never be re- 

 garded as a cause of rot, they must be looked upon 

 merely as a symptom. We cannot, however, say that 

 tubercles give rise to the liver-fluke, for tubercles are 

 often present in cases where flukes are absent ; and if 

 the latter were the effect of the former, their presence 

 under such circumstances would in all probability be 

 constant. 



III. Particular plants have been said to cause rot, 

 but the proofs of their evil tendencies being in every 

 instance about as logically supported as the fluke 

 theories already mentioned, I need not trouble myself 

 oi the reader by proceeding to details. 



Real Causes of Rot. Everything that has a ten- 

 dency to weaken the animal, will be more or less liable 

 to lead to rot. Exposure to cold and wet, mishaps at 

 lambing time, food bad in quality or deficient in quan- 

 tity, and over-driving, will all predispose the constitu- 

 tion to the deposition of tubercles. It is from the 



