APPENDIX. The Liver-Fluke; its effect on Sheep and other Graminivorous Animals-Flukes found in the Gall-ducts, in the Duodenum, and in branches of the Portal Vein, in Man. THE gall-bladder and gall-ducts of most of our graminivorous animals, and especially of the sheep, are frequently infested by two kinds of parasites-the Distoma hepaticum and the Distoma lanceolatum which are often found together, and are commonly confounded under the term liver-fluke. They are the cause of the distemper in sheep, which is known as the rot, and which is so justly dreaded by the farmer. The Distoma hepaticum is, in shape, very like a small sole or flounder, and, when full grown, is, in the sheep, from three-quarters of an inch to an inch and a half in length, and from one-third to half an inch wide, at the widest part. It has two suckers; hence the name Distoma. One of these is at the extremity of the head, (a) Fig. 18, and is a little turned downwards; the other (b), which is the larger of the two, is on the under surface of the body, at the base of the neck. The first leads to the alimentary canal, and is pierced by the mouth; the hinder one is imperforate, and is a mere organ of adhesion.1 Between the suckers, is a small depression (c), in which are the two genital pores. Fig. 18. Distoma hepaticum, from a sheep. The alimentary canal is, for a very short distance from the first sucker, a single tube, and then divides into two, which diverge a little to embrace the genital pores and the hinder sucker, and then run parallel to each other 1 See Owen's Lectures on the Comparative Anatomy of the Invertebrate Animals, from which the account of the anatomy of the liver-fluke in the text is chiefly taken. along the middle of the body to near the tail, where their ends are closed. These parallel tubes send off many branched tubes from their outer sides, which extend nearly to the margins of the body. The ends of all these tubes are closed or blind. The organs of both sexes are in the same individual. The male organs are situated between the alimentary tubes. Convoluted seminal tubes, which may be recognized by their opaque white color, occupy a great extent of the middle part of the body, and terminate by two trunks in a common canal, which ends at the base of the penis. The penis, when flaccid, is spiral, and not unfrequently may be seen projecting from the anterior genital pore. h f Fig. 19. d a Distoma Lanceolatum, magnified. a, b. The suckers. c, d, d. The alimentary canal. e, e. Male organs. ff. Ova ria. g, g. The ramified ute rine tube. h. Outline of D. lanceolatum, of natural size. -(Owen.) The ovaria occupy the whole margin of the body for a line in breadth. They consist of minute branched tubes in which the ova are developed. The oviducts terminate in a single large canal which opens by a distinct pore, immediately behind the male bursa, after making many convolutions between this and the hinder sucker. The body is soft, almost of gelatinous consistence, and semitransparent; and of a whitish color, variegated near the margins by the yellow ova, and within by the double ramified alimentary canal, which is greenish or brown from containing the coloring matter of bile. The Distoma lanceolatum, which was at one time regarded as the young of the Distoma hepa ticum, is much smaller, being commonly about a quarter of an inch in length, very seldom half an inch. It also differs in shape from the Distoma hepaticum. The outline of the body, instead of being rounded at each end, as in the latter, has each end lancet-shaped; the end terminated by the head being much the narrower or more pointed of the two. The sucking-cups are placed as in D. hepaticum, but are larger. There are also differences in the internal structure of the two varieties. In the D. lanceolatum, the alimentary canal does not ramify as in D. hepaticum. It is a single tube to the genital pore, which is here midway between the suckers, and then divides into two, which go along near the margins of the body, without sending off any branches, almost to the tail, where their ends are closed. male organs are contained in the anterior part of the space between the alimentary tubes. The ovaria are situated at the margins of the middle third of the body, outside the alimentary tubes. The oviducts run transversely and terminate in a common uterine tube, which is very long and tortuous, occupying all the hinder part of the space between the two alimentary tubes. The In sheep, these parasites are often found in great numbers. Many hundreds may sometimes be counted in a single liver. They produce remarkable changes in the gall-ducts they inhabit, and through them in the adjacent parts of the liver. The gall-ducts infested by them become dilated, and their coats much thickened. In cutting across the liver, after the rot has lasted for some time, many branches of the hepatic ducts are seen of the size of a large quill, with thick coats having much the look of soaked leather. These ducts are stuffed with flukes, and often with a dirty greenish matter, the excrement and ova of the flukes, enveloped in mucus. The ova are egg-shaped bodies, all nearly of the same size of an inch long, and about of an inch broad. Under the microscope, they are yellow by transmitted light, have a distinct single outline, and appear solid and filled with very fine granular matter. 200 At first, only the larger branches of the hepatic duct are changed in the way described. The smaller branches, which are not yet reached by the flukes, are healthy. It often happens, too, that, while some of the larger ducts are so changed, others contain no flukes, and are quite healthy. After a time, the infested gall-ducts are still more changed. Those near the under surface of the liver often form white tubes, the largest the size of the thumb, or larger, which project above the surface, and in some parts are visible, without dissection, quite to the edge of the liver. On the convex surface of the liver, the dilated tubes, being deeper-seated, are not visible except in a spot, here and there, near the edge. The coats of these white prominent gall-ducts are much thickened, and have the look and almost the toughness of cartilage. On tracing them from trunk to branch, we sometimes find one closed, or blind, at the further end, from obliteration of the smaller branches which went to form it. These blind tubes are filled with mucus and the remains of flukes, which die when deprived of the bile on which they subsist. It now and then happens, too, that a portion of a dilated duct becomes separated from the rest, so as to form a cyst, which is filled with mucus. Those parts of the liver in which the ducts are much dilated are more or less atrophied, from pressure and from obliteration of some of the small ducts, and are pale and shrunken, as compared with other parts of the same liver in which the ducts are less diseased. Occasionally, a thin false membrane is found on the convex surface of the most diseased portion of the liver, and uniting this by threads to the contiguous organs. Later still, the inner surface of the ducts becomes incrusted with chalky matter (carbonate of lime), which in the end transforms them into bony tubes. Now and then there is found a small cyst filled. with chalky matter and completely isolated from the tubes; the remains, perhaps, of what was at one time a mucous cyst. The effects which these parasites have on the health of the sheep are also very striking. At first the sheep has a remarkable aptitude to grow fat, and, if the accumulation of fat only be regarded, may be prepared for the butcher perhaps weeks sooner than a sheep perfectly sound. This circumstance has even been turned to profit. Sheep nearly ready for slaughter have been purposely placed in a pasture that gives the rot, that they might fatten more quickly. But unfortunately, while they grow fat, their muscles waste, and, from the first, they are weak and languid. They soon become anemic, and now and then slightly sallow. They are recognized by butchers as having the rot, chiefly by an unusual whiteness of the eye, which does not show the red vessels seen in the eye of a healthy sheep. The caruncle, too, at the corner of the eye, is pale, and often slightly yellow; and the skin, when the wool is parted, does not exhibit the ruddy hue of health, but is pale and sometimes sallow. There is also a tendency to oedema, which is first conspicuous in dropsical swelling of the legs just above the hocks: but before this appears, the skin is looser than in a healthy sheep-it is more readily stripped off by the butcher.' As the disease goes on, the fat disappears, and the animal loses flesh rapidly, and grows extremely feeble. The appetite fails, and the bowels are irregular; sometimes costive, at other times much purged. The oedema increases, the skin in consequence becomes loose and flabby, and gives out a peculiar crackling sound when pressed, and the belly also gets dropsical. The wool now comes off 1 These symptoms from being so obvious were early noticed. They are pointed out very distinctly in the famous Booke of Husbandrye, published more than three centuries ago (the Booke of Husbandrye, by Sir Anthony Fitzherbert, 1532), when, from the general want of draining, the rot must have been more destructive in this country than now. "Take both your handes, and turn up the lid of his eye, and if be ruddye and have red stringes in the white of the eye, then he is sound, and if the eye be white like tallowe and the stringes dark coloured, then he is rotten." "And also take the shepe upon the wol on the side, and if the skin be of a ruddey colour and dry, then is he sound, and if it be pale-coloured and watery then he is rotten" -(Library of Useful Knowledge. Treatise on the Sheep, p. 446.) at the slightest pull, the skin often becomes spotted with yellow or black (probably from ecchymosis), and the animal dies a mere skeleton-generally from two to six months from the commencement of the disease. The rot, however, is not inevitably fatal. Sheep frequently recover, if early removed to a healthy pasture. It will at once be seen that the chief symptoms of the disease, and its fatal issue, depend not so much on the changes of structure in the liver, striking as these are, as on an unhealthy state of the blood. The disease may prove fatal, when part only of the liver is involved, and when more than enough is left for all the purposes of secretion. The sallowness of the caruncula lachrymalis and of the skin, occasionally noticed, is always slight, never amounting to jaundice, and depends probably more on anemia than on bile. The blood becomes impoverished in this disease just as it does from granular degeneration of the kidney, in man. The paleness of the conjunctiva and of the skin, that may be noticed even at an early period, show diminution in the proportion of globules in the blood. M. Andral has ascertained that, when the disease has gone on to dropsy, the proportion of albumen is likewise much diminished, and he considers this circumstance to be a strong argument in favor of the opinion he has advanced, that the dropsy from granular kidney, and in this disease as well, is caused immediately by loss of the albumen of the blood. In sheep infested with flukes, the kidneys are pale like the other tissues, but not otherwise altered in structure; and the urine does not contain albumen. The yellow and black spots on the skin often noticed in the advanced stage of the disease, if they result from hemorrhage, as they probably do, would favor the inference that at this date the proportion of fibrine in the blood is also diminished. The blood becomes at length so drained of all its organic constituents-globules, albumen, fibrine-that it is no longer fit to nourish the body and maintain life. The death of the animal is hastened by diarrhoea, which recurs frequently, especially towards the close of the malady, occasioned probably by irritating matters passing into the intestines from the gall-ducts. No one, I believe, has inquired, how flukes in the liver work this change in the blood. It cannot be by merely consuming the bile, unless this is much more necessary for digestion in sheep than in man; and flukes have no organs which can enable them to penetrate |