Diseases of Sheep. 



309 



the question still remains in what this fatal peculiarity of soil con- 

 sists. This question is rendered more diflicult of solution by the 

 capricious exemption of particular districts from this pestilential 

 disorder. In some of the marshy pastures of Kent, such as the 

 Isle of Sheppey, where the ague is prevalent, the rot is but little 

 known, and generally throughout that county is rarely met with. 

 The same fact may be stated of Romney Marsh and of the Essex 

 marshes, an exemption which may possibly be, in some measure, 

 explained by their proximity to the sea. The South Downs of 

 Sussex are also said never to have been visited by the complaint. 

 But this exemption is not peculiar to large districts ; on the same 

 farm some pasturage will rot sheep, while other meadows will 

 j)roduce no mischief. Even in ground that is underdrained, and 

 presumably dry, sheep will be affected, some part of the soil being 

 perhaps light and porous, and hence easily drained, while other 

 parts that are heavy and clayey, though the drains are no farther 

 apart, retain lodgements of wet, from which a pestilential exhal- 

 ation proceeds. Observation, however, has led to the conclusion 

 that whatever may be the poisonous matter, whether animal or 

 vegetable, the existence of it is immediately consequent on moist 

 or wet weather, especially if followed by warm suns, while dry 

 weather returning prevents the disorder spreading. It has also 

 been noticed that wet pasturage, as such, does not generate the dis- 

 order ; that sheep have been fed in meadows adjoining to rivers, 

 and in fields with ponds in them, without infection, though con- 

 stantly exposed to wet ; but that, when the process of exhalation 

 begins, these very pastures, though previously innocuous, become 

 capable of exciting the rot.* 



It has been stated, on good authority, that the fatality of the 

 climate of Sierra Leone, and perhaps of many other tropical comi- 

 tries, begins at that period of the year when vegetation, having 



* My own opinion ditFers from that of the Author, respecting the cause of 

 rot in sheep, although I am happy to say that we know little of the disease 

 in this part of the kingdom. But I have twice had the rot make its appear- 

 ance with me, and both times it has occurred when the sheep have been 

 made in a field the whole of which was wet ; for although my sheep have 

 always been allowed to go into the same field, the disease has never attacked 

 them but twice, the first time being the accidental consequence of their being 

 confined in this particular field, when fatting, and the whole of them proving 

 to be affected with rot ; and the second, when I tried in the following season 

 the experiment of inclosing a few more in the same place, the result of which 

 was the occurrence of the disease in the greater part, hut not the whole of 

 them. From these facts, and much consideration of the subject, I have 

 formed the opinion that sheep get the rot in the greater number of cases 

 from the circumstance of being compelled to lie on wet ground ; for when 

 they have been at liberty to range into other fields adjoining the marshy 

 one referred to, and could thus obtain dry resting-places, although fedchielly 

 on the wetland, I have never found a single sheep deficient. — W. Greaves. 



