. Diseases of metabolism and of the blood, animal parasites, toxicology. Constitutional diseases; Metabolism; Blood; Medical parasitology; Poisons. Fig. 32.—Distomum TREMATODES 509 of a considerable size: Breadth to mm., length to mm. The anterior pole is flatter and has a lid. The development of the liver-fluke, explained by Leuckart and Thomas, is a very complicated one. The ova are discharged with the feces. After a pro- longed stay in water, the elongated miracidium develops and after some time breaks the cover of the egg. By means of its ciliary sac it floats about, a
. Diseases of metabolism and of the blood, animal parasites, toxicology. Constitutional diseases; Metabolism; Blood; Medical parasitology; Poisons. Fig. 32.—Distomum TREMATODES 509 of a considerable size: Breadth to mm., length to mm. The anterior pole is flatter and has a lid. The development of the liver-fluke, explained by Leuckart and Thomas, is a very complicated one. The ova are discharged with the feces. After a pro- longed stay in water, the elongated miracidium develops and after some time breaks the cover of the egg. By means of its ciliary sac it floats about, and finally is taken up by its first intermediary hosts, small water snails, the limnaeus minutus and limnseus cahuensis, which are found in large numbers in small pools. In this host the miracidia become transformed into sporo- cysts, which are generally found in the respiratory cavity of the snail. The sporocysts produce a second genera- tion of germ tubules, redia, from which, finally, the true young of the distoma develop in the form of caudate cercaria. The cercaria then emerge, adhere to grass and HEPATicuM'LiNNi"' water plants and, with these, enter their final host in an encysted form. From the intestine they migrate into the bile-ducts, where they develop into mature animals; It is obvious, in view of this mode of development, that man is but rarely inhabited by distoma, and even then only by a small nitmber. The entrance of the cercaria into man occurs principally by their ingestion with polluted drinking-water or with raw vegetables, salad, or water-cress, which have grown in inundated places. In many other ways they may enter the body; we need only consider how often children and even grown people put meadow-plants into the mouth. , About 18 cases of disease of the liver in- man from distoma have been re- corded. As only very few parasites were present, no special symptoms were caused inthe majority of these cases. Yet the cases of Bostroem and Biermer, in whi
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