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xxix] variety of sources, i.e. vegetables, water, etc., can be made to assume pathogenic properties. Further, following Frosch's methods, they succeeded in cultivating intestinal amœbæ by adding to the cultural media the bacteria usually associated with these amœbæ in the intestine, and which seem to exercise a necessary symbiotic or, rather, metabiotic action, i.e. modify the culture medium in a way favourable to the amœbæ. They have also shown that by gradual habituation amœbæ can be brought to withstand a degree of acidity greatly in excess of that normally present in the human stomach. These observations have not been confirmed, at least as regards the pathogenicity of saprophytic amœbæ. The pathogenic amœbæ have not yet been cultivated.



When present in stools, the amœbæ (Fig. 80) are generally easy to find. All the preparation necessary is to pick out a small fragment of stool shortly after it has been passed, and then to lay this on the slide and compress it sufficiently under the cover-glass to form a fairly transparent film. They are said to be most readily found in the watery stools produced by a saline purgative; doubtless because they are washed from off the surface of the bowel by the action of the drug. In hot weather a warm stage is