120 The Common Liver Fntozoon of Cattle. 



stance has suggested the common practice of mixing salt with 

 the food of sheep and cattle, both as a preventive and curative 

 agent ; and there can be little doubt that this remedy has been 

 attended with more or less satisfactory results. The intelligible 

 explanation of the good effected by this mode of treatment we 

 shall find to be intimately associated with a correct under- 

 standing of the genetic relations of the entozoon in question, for 

 it is probable that the larvas of Fasciola hepatica exist only in 

 the bodies of fresh water snails or small aquatic animalcules. 



It is not intended in the present communication to offer a 

 lengthened account of the various discoveries and facts which 

 enable us to make this last-named statement ; but correlating all 

 the known data afforded by the experience of the parties above 

 mentioned, by observant naturalists, by our own researches, and 

 more particularly by the recent experimental investigations of 

 continental helminthologists, we shall provisionally state in a 

 tentative manner the conclusions to which a due consideration 

 of all these facts inevitably lead. The deductions here recorded 

 may eventually require modification in respect of their minor 

 details, but in the main they will be found substantially correct, 

 and therefore be likely to convey that kind of information 

 which can scarcely fail to interest those more immediately con- 

 cerned in the preservation of cattle : — 



1. The Fasciola hepatica, or sexually mature liver- fluke, is 

 especially prevalent in sheep during the spring of the year, at 

 which time it constantly escapes from the alimentary canal of 

 the host, and is thus transferred to open pasture-grounds. 



2. It has been shown by dissections that the liver of a 

 single sheep may, at any given time, harbour several dozen 

 specimens of the fluke, and it is certain that every mature en- 

 tozoon will contain many thousands of minute eggs. 



3. The escaped flukes do not exhibit powers of locomotion 

 sufficient to prove them capable of undertaking an extended 

 migration, but their movements may subserve the purpose of 

 concealing them within the grass or soft soil where they have 

 fallen. Their habit of coiling upon themselves probably facili- 

 tates the expulsion of their eggs. 



4. The eggs can only escape from the oviduct of the ento- 

 zoon one at a time, but there is every reason to believe that 

 large numbers of loose ova are expelled from the infested sheep 

 in the same manner as the flukes themselves. 



5. By the dispersing agency of winds, rains, insects, feet 

 of cattle, dogs, rabbits, and other animals, and even by man 

 himself, the eggs are carried in various directions, not a few of 

 them ultimately finding their way into pools, ponds, ditches, 

 canals, and running streams. 



