ON THE SHEEP OF ZETLAND. 267 



jially imported into the country, and is at present 

 propagated by contagion, is strictly correct. This 

 opinion derives strength from different circum- 

 stances. The period of the first appearance of 

 the disease, is fresh within the memory of many, 

 and the fact is related by persons of unques- 

 tionable veracity, and accuracy of observation; 

 and it has been found to spread itself from the 

 place where it first occurred, as from a centre. 

 There are several parts of Zetland into which it 

 has never yet found admission, although separated 

 from those in which it rages, by a narrow ferry 

 only. This fact supports the idea of a contagi- 

 ous principle. Were the disease in general the off- 

 spring of external causes, occasional instances 

 would certainly be produced, although neither so 

 frequent nor so numerous as in situations where 

 their presence is more uniform. 



From a general view of the usual progress of 

 blindness in sheep, as mentioned by different 

 writers on the subject, I am disposed to believe, 

 that the pathology of the different affections is 

 not always well understood. In some cases there 

 is genuine ophthalmia, when the inflammation ex- 

 tends from the conjunctiva all over the lucid 

 cornea. This is among the worst species of the 

 affection, and it requires the most energetic treat- 

 ment. But in those instances, where " a blue 

 " slough covers the whole of the eye, without any 

 ?' admixture of red vessels," as mentioned by Mr 



