6 The Sheep-Fluke. 



impressive thau if reserved and presented in proper connection, and as a 

 whole. This, however, is a matter that concerns the investigator more than 

 it does the public whose servant he is, and any public scientific officer who 

 reserved his results for this reason alone would be justly criticised. 



In deference to this latter fact, and the wishes of his confreres, the author 

 submits the following fragmentary observations, with the hope that they 

 may yet appear in a more connected and extended form in a general work 

 on Australian parasites. 



Brief Eesume of our knowledge of the Sheep-fluke. 



Our knowledge of the eheep-fluke extends back into remote antiquity, and 

 though the older observers knew the disease caused by the fluke rather by 

 its effects than through its cause, it is beyond dispute that at a very early 

 date the disease was assigned to its true cause — a flat, worm-like parasite 

 found in the liver. No doubt other diseases, such as anthrax, were con- 

 founded by the ancients with the true liver-rot, as it was often called ; but 

 this fact does not obscure the other fact that the parasite was known as the 

 cause of a fatal disease contracted on wet and swampy ground. 



As it is the object here to be as brief as convenient, no mention will be 

 made of the numerous and vast epidemics of the past that have swept off 

 sheep by thousands, — it is said even by millions. These details and many 

 others will be left to be dealt with on later pages. Let our first object be 

 to get an accurate general view of the subject, regardless of the less impor- 

 tant details. Suffice it to say, then, that whenever these epidemics prevailed, 

 they were accompanied by unusual circumstances of weather or pasturage, 

 and the livers of the dead sheep were invariably foiiud crammed with 

 fluke. {See Y\g. 6). 



These flukes were flat worms, of a flesh or darker colour, capable of 

 varying their shape, but for the most part having a somewhat spade-shaped 

 contour. Some hundreds of these were often found in the gall bladder and 

 ducts of a single liver. 



The observation of practical men soon taught them to associate the un- 

 usual prevalence of fluke with damp seasons and swampy pasturage, and it 

 was observed that even cattle and other stock grazing on such ]and became 

 more or less infected with the fluke (always in the liver), though these other 

 animals did not suffer so severely as sheep. The list of animals subject to 

 fluke grew until a dozen or more widely different vertebrates, including man 

 and marsupials, were included in it. 



The attention of scientific men having been drawn to this curious parasite, 

 they soon proved that each fluke produced a vast number of microscopic 

 eggs, and that these were to be found in the gall and contents of the intes- 

 tine, and that they passed into the outer world encased in the dung. What 

 became of them afterwards no one for a long time could say. 



Tears went by ; microscopes were improved, and became more numerous ; 

 and at last some acute observers began to remark on the similarity in form 

 of certain so-called animalcules found in snails to the younger stages of 

 fluke found in sheeps' livers. Later on, the same and other new observers 

 attracted to the subject found that these animalculse in the snail were tlie 

 progeny of other animalculse, also found in the snail, and that these latter 

 again came from another animalcule to be sometimes found swimming free 

 in the water of the pools where the snails abounded. All these discoveries, 

 however, were so novel and bizarre that there was a long period of waiting 



