Fig. 32. — Distomum 



TREMATODES 509 



of a considerable size: Breadth 0.075 to 0.09 mm., length 0.14 to 0.15 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 which the fatal outcome of the disease was due to the parasite, prove that 

 even a single parasite may produce severe phenomena. 



It seems that the parasites remain latent for considerable time. The 

 general condition of the patient changes gradually for the worse, he ema- 

 ciates, obstinate jaundice and uncontrollable, sometimes hemorrhagic, diar- 

 rhea develop. Then follow vomiting, violent pains in the region of the 

 liver and general dropsy until, with progressing cachexia, death takes place. 

 The autopsy often shows numerous changes in the liver: Enormous dilata- 

 tion and occlusion of the bile-ducts with ulceration of the same; excessive 

 increase of the connective tissue in the area surrounding the focus of the para- 

 site; obliteration of the large bile-ducts, occlusion of the hepatic duct, etc. 

 If, therefore, the diagnosis should be difficult, an examination of the stools 

 will enable the physician to recognize the disease. Bostroem and Perroncito 

 succeeded in finding the ova of distomata in the stools. 



Owing to the difficulty of the diagnosis, the treatment must always remain 

 symptomatic; but if the diagnosis be correctly made, the expulsion of the 

 liver-fluke may be attempted by the administration of mineral waters or other 

 remedies promoting the secretion of bile. 



