FLUKE, or Fr.unE-wowst, Distoma hepaticum, an entozoon common in the liver and biliary ducts of ruminants, particularly of sheep, in which it produces the disease called rot, often causing great mortality in flocks during. wet seasonS„and on „ill-drained lands.
It receives its common name from its resemblance in form to the flounder, of which fluke is a Scotch and old English name. For a similar reason, it is sometimes called plaice. It is a trematode (q.v:) worm, higher in organization than the cestoid worms; but not so high as the ccetelmintha. It is generally not quite an inch in length, often much less, but sometimes more; of an oval form, its breadth about half its length; flat, in color not very different from the liver in which it exists: it has no eyes nor other known organs of special sense; it is hermaphrodite, and the organs of reproduction occupy great part of its body, the ovaries being ranged along the margin ; its anterior extremity is furnished with a sucker, and another is situated at a small distance on the ventral surface, whence the name distoma (Gr. two-mouthed), but the terminal sucker alone is perforated, and serves as a mouth, by which bile—the food of the creature—is imbibed; the tube which proceeds from it not, however, beccfming a proper intestinal canal, but soon dividing into two large branches, and ending in minute ramifications in all parts of the body. Prodigious numbers of flukes are sometimes found in the liver of a single sheep, and of very different sizes, but they are now believed not to multiply there as was formerly supposed. Their eggs, indeed, are produced there in great quantity, but find their way into the outer world to begin a series of transformations not yet very accurately traced with regard to this particular species, but of which the general nature is known. See
CERCATUA, TREMATODE WORMS, and GENERATIONS, ALTERNATION OF. It Seems that the young flukes, having entered as cereariee into the bodies of mollusks or of aquatic insect larva;, are conveyed into the stomachs of ruminants feeding on herbage to which these are attached, and finding their way to the liver, there attain their full development. See ROT. • Instances have occurred of the presence of di-stoma hepaticum in the human liver and Dena porta; as well as of a similar species, D. lanceolatum; a small species of the same genus, D. heteropllyes, has been found in great numbers in the human intestines in Egypt, but its influence on the system is unknown; a species of much elongated form, D. lama tobium, is very common in Egypt, infesting the vena porta of man, and the walls of the urinary bladder, and producing local, and afterwards general disease; a small species, D. ophthalmobium, has been found in the human eye, but probably through some such accident as in another case has led to the occurrence of the common F. under the skin of the foot, where it caused a sore. Of all the known species, the Egyptian, D. llama tobium, is by far the most hurtful, as infesting the human body. This species is also remarkably different from the others, in not being hermaphrodite, and in the extreme dissimilarity of the male and female; the female being a thread-like worm, for which a lodgment is provided in a furrow (gynceeophorus) on the ventral surface of the male.
The genus distoma or P. contains a great number of species, infesting, in their mature state, different kinds of animals, and finding their appropriate place in very different parts of the animal frame. The wrinkled membrane around the eyes of birds is the place of some.