554 SPOEADIC DISEASES. 



These opinions are entitled to some consideration, as it is an 

 actual fact that the mortality is very much greater after a 

 sudden change, particularly — and in every instance that came 

 under observation during the investigation — a change from warm 

 to cold and inclement weather. 



But neither change of weather nor exposure to its inclemency 

 are of themselves sufficient to induce the disease, nor does the 

 latter in any of its phases simulate an ailment brought about 

 by climatic influences ; and the only conclusion that can be de- 

 duced from the above premises is, that inclement weather, by 

 its debilitating influences, predisposes to disease, and causes 

 many animals to succumb to what otherwise might have passed 

 off without very grave consequences. 



One flockmaster observed that he believed the great majority 

 of the sheep in an infected district had the disease once in their 

 lives in greater or less severity during the season ; that if the 

 food were good and the weather favourable, but few became 

 seriousl}^ ill, and fewer died ; but if the weather became sud- 

 denly cold or wet, the disease was able to make a deeper 

 impression upon the animal body, and many then succumbed ; 

 and further, if the disease were due to the weather, why was it 

 confined to certain districts, whilst in others equally cold and 

 exposed it was entirely unknown ? 



Being satisfied that the grasses, geological formations, and 

 weather were insufticient to cause the disease, one other pro- 

 bable source of it remained to be considered, namely — 



III. The inflitence of fields {Ixodes). — The belief is general 

 amongst all acquainted with louping-ill that it is closely allied 

 to ticks ; the majority of farmers, indeed, believing that the 

 parasites, by fixing themselves in the skin and sucking the 

 blood, cause such extensive irritation, pain, and weakness, that 

 the animals perish from these causes, and that the convulsive 

 spasms and paralysis are merely symptoms of irritation and 

 debility. A very brief acquaintance with the disease, however, 

 compelled the author to conclude that, no matter how closely 

 allied the tick and the disease were, irritation and loss of 

 blood had little or no connection with tlie disease under con- 

 sideration ; for in many instances but few of the parasites were 

 found on some of the diseased sheep, whilst many healthy ones 

 were swarming with them, and seemingly feeling but little dis- 



