272 ON THE SHEEP OF ZETLAND. 



. The Rot, known in Zetland by the name of 

 mua sickness, is also one of the diseases with 

 which the sheep are frequently affected. Various 

 opinions have been entertained, respecting the 

 cause and seat of this disorder. Dr Coventry, 

 with great propriety, conceives, that the most 

 common species of it arises from deficient and de- 

 praved aliment, and that it somewhat resembles 

 the scurvy in the human species *. I am per- 

 suaded, that this view of the subject is correct, as 

 applied to Zetland, where the causes assigned for 

 its production so often exist, and I am inclined to 

 believe, that the affection of the liver should be 

 viewed rather in the light of a secondary symp- 

 tom. The general debility induced by the com- 

 bined effects of cold, moisture, and depraved 

 aliment, lays the foundations of glandular ob- 

 structions and dropsical affections. The liver 

 suffers with the other organs, and becomes the 

 seat of a peculiar species of hydatid, in which an 

 insect (fasciola hepaticaf) is usually contained ; 

 but the presence of the insect in the liver, al- 

 though a frequent concomitant of the rot, is not 

 absolutely essential to its existence. 



* Introductory Discourse. 



f This insect is of a flat circular form, and often three 

 quarters of an inch in diameter. It flaps vigorously on 

 a table, when removed from its nidus. 



