DISEASES OP THE OX AND SHEEP. 457 



uever troubled with flukes. This may be due to the limneeus 

 possibly not thriving in places where salt abounds in the soil. 



Now the liver-fluke, known scientifically as the Fasciola 

 hepatica, is a member of the large class Vermes, of the sub- 

 class Sterelmintha, and it belongs to the order of Trematoda or 

 flukes. 



Now, the " Trematoda," or " flukes," as already said, are a 

 group of worms embracing several different families, and they 

 are possessed of either one or more suckers. The term " fluke " 

 itself is of Saxon origin, and indicates flatness. Although, 

 however, the ordinary liver-fluke is flat, the members composing 

 many species of the order are round, bi-convex, or even filiform. 

 The ordinary liver-fluke [Fasciola hepatica) is not usually more 

 than an inch in length. 



The digestive system is seen to consist of a short oesophagus 

 from which the double and tree-like stomach branches into 

 every part of the body, the ramifications terminating in blind 

 extremities. The contents consist principally of bile which 

 has been absorbed from the gall-ducts of the host. 



This worm usually passes the adult stage of its existence in 

 the liver, bile-ducts, or gall-bladder of a sheep, or of almost any 

 ruminant, or of some one of certain other animals, of which we 

 may mention the goat, argali, every variety of the common ox 

 and zebu, zebra, two-humped camel, horse, ass, antelope, gazelle, 

 red-deer, roe-deer, and the fallow deer, pig, hare, rabbit, squirrel, 

 goose, pigeon, pheasant, poultry, great kangaroo, beaver, and 

 man himself, in all of which it has been found, while a much 

 larger but closely allied species, known as the Fasciola gigantea, 

 infests the giraffe. 



All these animals may sufi'er from the disease known as ** rot,'"* 

 which is produced by the presence of flukes in the liver. The 

 various phases of existence through which the worm passes are 

 numerous and complicated. 



It seems a startling statement to make, but it is nevertheless 

 true, that a single fluke may produce half a million eggs, while 

 each e^o^ may give rise to 200 cercarise ; aud thus one fluke 

 might, if every circumstance was favourable, yield 100 million 

 flukes! Now, one sheep may be infested with a thousand flukes, 

 and hence one sheep may give rise to one hundred thousand 

 million flukes ! In the season from 1830 to 1831 the estimated 



