DISEASES OF SHEEP. 



329 



parasites destroyed several .times as many in Australia. Unfor- 

 tunately we have it with us, but not nearly to the same extent; 

 probably Because of the muca smaller proportion of sheep to our 

 vastly greater territory. The history of -this parasite is quite simi- 

 lar to that of other injurious enemies of the sheep as the tape 

 worms for instance in that it needs an intermediate bearer in 



FIG. 9. Mature Fluke. 



which to pass the first stage of its existence. This is a mollusk, a 

 species of snail, which inhabits fresh water marshes. The curious 

 history of this parasite is of great interest to the American shep- 

 herd, because we have the bearer of it here and the creature itself. 

 It is comparatively abundant in the marshes of the Northwest 

 and has been found in the States of New York and Pennsylvania. 

 In the former locality it has been found in the livers of deer and 

 rabbits; and in rabbits in Pennsylvania. It has also been found 



FIG. 10. FIG. 11. FIG. 12. 



The Fluke Egg. Egg with Embryo. The Embryo. 



FIG. 13. 

 Snail Enlarged. 



in the flock of Southdowns owned by the late Royal Phelps, on 

 Long Island, N. Y.; but in this case the parasite was unquestion- 

 ably imported in the sheep, which were Southdowns presented to 

 Mr. Phelps by an English friend. This introduction of the pest 

 was doubtless successful in establishing it in that locality; as three 

 years had elapsed since the sheep had been imported. 



The mollusk in which the fluke passes its larval stage is a 

 snail, but it is not that the sheep devour the snails, and so take 

 up the parasite, but the young of the fluke are taken up by the 

 sheep as they drink at stagnant ponds or water holes in marshy 

 ground, where in an intermediate stage they pass a portion of their 

 existence. Then, finding their way from the stomach, to the liver, 



