568 ON THE ROT IN SHEEP. 



autumn often produces, is a very sure way for producing the 

 disease. 



3. The words just given in inverted commas are not the exact 

 words employed by my informants ; those which follow are, or 

 pretty nearly so — * a single bellyful will give the disease.' 



4. * A pasture will give the disease at the back-end of the year 

 which won't give it after Candlemas.' This means that the winter 

 cold and rains destroy or wash away the larval or other forms of 

 flukes which the slugs brought with them in the autumn. 



The first of these observations is, like all other observations and 

 all experiments concerning the matter with which I am acquainted, 

 utterly destructive of Dr. Harley's suggestion as to the self- 

 infection of sheep from their own droppings or those of their 

 fellow sheep. If this were possible why should it not take place 

 on the uplands or ' commons ' — as the Lake shepherds call the 

 unenclosed mountains — where the sheep, for the sake of food on 

 those often limited grazing spaces or ' alps,^ or for the sake of 

 shelter, often huddle together as closely as they do or can do any- 

 where else? It is destructive also of the often -uttered ascription 

 of rot to damp and moisture, the mountain ridges of Westmoreland 

 being ' many-fountained ' to a degree never dreamed of by Theo- 

 critus in Mediterranean districts, or realised by our own Laureate 

 out of these ' rainy isles.' It is, on the other hand, confirmatory, as 

 are all accurate observations on the subject, of the view which 

 asserts that the presence of snail or slug is a necessary factor in 

 the causation of rot. Snails and slugs are but scantily represented, 

 if present at all, on mountain tops ; there are no slugs in Forbes' 

 and Tschudi's lists of high Alpine ranges ; and these districts, like 

 salt marshes, owe their character for considered ' soundness,' as the 

 phrase is, as regards the most destructive of sheep diseases, to this 

 absence or paucity of, at least, certain mollusca. 



I was first put in this pursuit upon the slimy trail of the slugs 

 and snails specified by various well-known facts which it is here 

 unnecessary to specify. The number of the mollusca which it is 

 necessary to trouble about appears to me to be very distinctly and 

 very conveniently limited by the fact pointed out by the late 

 Willemoes-Suhm, one of the ' good company of famous knights ' 

 upon H. M. Challenger, as to the Faroe Islands. The Faroe 

 Islands are afflicted by the rot, but they have only eight snails and 



