THE LIVER FLUKE. 



221 



a highly organized animal. It possesses a branched intestinal 

 canal arid digestive organs, seen at figure 80, and a fully devel- 

 oped circulatory system seen at figure 81. These figures are life- 

 size. The fluke possesses the power of self-impreg- 

 nation should a second individual not be present 

 for copulation. It propagates by means of eggs, 

 which are produced in great numbers, and which 

 pass with the bile into the intestinal caDal, from 

 whence they are voided with the dung of the sheep. 

 Fig. 79. rp^ 6 gg S nee( j to k e -Cashed by ra i n O r flood into 



stagnant water to become developed. The embryo, covered with 

 ciliae or arms the locomotive organs leaves the shell and swims 

 in the water. It is then believed, from our present knowledge of 

 its habits, to penetrate the bodies of snails or other amphibious 

 molluscs, and thus pass a stage of its existence. These soft-bodied 

 molluscs being swallowed by the sheep which graze in low, moist 

 pastures, along with the herbage ; the parasites contained in them 

 are introduced into the stomach, 

 from which they pass by the 

 gall ducts, into the liver, and 

 thus complete the round of their 

 existence. They collect hi 

 masses, sometimes closely pack- 

 ed in the gall ducts, obstruct the 

 flow of the gall, and set up 

 irritation, and thus produce 

 jaundice, by which the mem- 

 branes are colored yellow. At 

 this first outset of the disease 

 the sheep seems to thrive and 

 make fat rapidly, but the fat is 

 highly colored, especially that of the kidneys and brisket. Some 

 English feeders have purposely exposed their sheep to the flukes 

 to hasten the fattening. But this stage passed, the structure of 

 the liver becomes changed from the irritation and pressure ; the 

 gall ducts become enlarged into extensive cavities, which are filled 

 with flukes and their eggs. The pain thus caused makes the ani- 

 mal restless and thin. The partial destruction of the liver, and 

 stoppage of its functions, causes diarrhea, dropsy, and the disor- 

 ganization of the blood, which constitute the fatal rot. The 

 course of this disease is rapid. At the latter end the whole system 

 is deranged. The breath is offensive, a deep distressing cough with 

 fever racks the animal, the skin is covered with yellowish and 



Fig. 80. 



Fig. 81. 



