214 DISEASES OF SHEEP. 



This examination of the sheep will lead us to tlie principal and 

 primary seat of the disease, namely, the liver. What is the cause of 

 this affection of the liver is another question, and a very important 

 one. There is a dispute which no one has yet settled, whether this 

 fluke-worm is the cause or the consequence of the disease. I am 

 very much inclined to think that it is the consequence, although it 

 may and does much aggravate the disease. These parasitical ani- 

 mals, botli in the animal and vegetable kingdoms, fasten upon a part 

 that is diseased, or the vitality of which is weakened. 



Another disputed point is the source of these flukes. Are the eggs 

 taken up in the herbage ? Does some insect or fly, that is a fluke in 

 one part of its existence, lay its eggs on plants growing in wet pas- 

 tures, or by the side of stagnant water ? We have no proof of this, 

 and we never saw the fluke in any other form. Therefore, it is use- 

 less to dispute about that which cannot be resolved. The most pro- 

 bable thing, however, is, that the eggs, whence the fluke is produced, 

 are, like the eggs of many animalcula, floating in the air, so small 

 and pellucid as to be invisible to us ; that they are inhaled with the 

 breath, or received with the food, but only find a proper nest, a proper 

 place to be hatched into life, in the liver of the sheep labouring under 

 the rot. 



These flukes are occasionally found in the livers of almost every 

 domestic quadruped, and so far as it has hitherto appeared, they are 

 in all of them connected with disease. 



Well, then, what is the cause of this affection of the liver 1 It is 

 evidently connected with moisture, although it may be difficult to 

 trace the connexion between this moisture and a diseased liver. 



It is, however, proper to observ-e, that the eggs of flukes have been 

 found in countless numbers in the biliary ducts on examining the 

 liver of a cothed or rotten sheep in the months of April, May, or June ; 

 and it is considered by respectable authority, that these eggs are 

 passed into the bowels, evacuated with the dung, and, their vitality 

 being preser^^ed by the sun and moisture, they are swallowed with 

 the grass by sound animals, who thus become infected. Whereas 

 if the eggrs had fallen on dry land, their vitality would be destroyed. 

 Although it appears reasonable enough that the infection is produced 

 through the medium of the stomach, yet it would be expected, if the 

 above" theory were entirely correct, that by keeping sheep from rot- 

 ting land for several years, such land would cease to produce the 

 disease, from the absence of the eggs; which, however, is not found 

 to be the case. It is therefore probable that there are other sources 

 from which the eggs of flukes are derived, besides the dung of sheep. 

 The history of the rot is plain enough here. It prevails, or rather 

 it is found only, in boggy, poachy ground. On upland pasture, with 

 a light sandy soil, it is never seen ; and in good sound pasture, in a 

 lower situation, it is only seen when, from an unusually wet season, 

 that pasture has become boggj^ and poachy. It is also proved to 

 demonstration, that land that has been notoriously rotting ground, has 



