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XXIX] whole extent with a mass of ulcers from which hang shreds of necrotic tissue— lesions resembling those of amœbic dysentery.

In the treatment of balantidial dysentery Walker finds from his experimental work that organic compounds of silver are the most effective. Barlow recommends methylene blue in 2-grain doses three times a day for not less than ten days.

Besides E. histolytica, E. coli, and B. coli, certain other protozoa occur from time to time in the intestinal canal and appear in the fæces. Of these, perhaps Lamblia intestinalis has the best claim to be regarded as of pathological importance. Its usual habitat is the upper part of the small intestine. When newly passed in the fæces it is very active,presenting a characteristic appearance (see p. 939). Lamblia infection is associated at times with a type of recurring diarrhœa accompanied with abdominal discomfort and the passage of mucus in which the free form of the parasite may be found in vast numbers. On recovery from one of these attacks only the encysted form of the lamblia can be found. Drugs, including emetine, have hitherto failed to eradicate this parasite, which may continue to appear in the stools, either in the flagellate form or encysted, for many years. Trichemonas intestinalis, though more common than the foregoing, has less, if any, claim to pathogenicity. Its presence seems to be favoured by conditions in which diarrhœa or fluidity of stool is a feature.*

The germs of dysentery often water-borne.— Notwithstanding the vast amount of speculation, time, and work expended in endeavouring to ascertain what the germ or germs of dysentery may be,