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504 resistance of the bowels, such as the depressing or congesting effects of chill, bad food, purgatives, intemperance, intestinal nematodes and trematodes. These prepare the ground for the action of (2) specific germs which have their action supplemented subsequently by (3) the ordinary bacteria of suppuration and ulceration. It must be with the mucous membrane of the bowels in these respects as it is with the skin of the surface of the body. For example, a traumatic erythema leads to a specific eczema which, in turn, may end in an ulcer. So with the bowel: a debauch, a chill, or bad food may lead to an intestinal catarrh. A specific germ, which in healthy conditions would not have proved pathogenic, coming on the scene produces a lesion of the mucosa, in which the ubiquitous pus germs find their opportunity.

Three types of dysentery, correlated to three different kinds of parasites, are now fairly well made out. These are not mutually exclusive; one type may be superposed on and complicate another. That there are other dysenteries, similarly correlated to parasites as yet unrecognized, is not to be doubted. The principal recognized types and their respective parasites are as follows:

1. BACTERIAL— Bacillary dysentery:
 * Bacillus dysenteriœ, (Shiga and Flexner).
 * Bacillus pyocyaneus.

2. PROTOZOAL —
 * Amœbic dysentery:
 * Entamœba histolytica (tetragena).
 * Balantidium dysentery:
 * Balantidium coli.
 * Kala-azar dysentery:
 * Leishman- Donovan body.
 * Malarial dysentery:
 * Malaria parasites.

3. VERMINOUS—
 * Schistosomum japonicum.
 * Schistosomum hœmatobium.
 * Schistosomum mansoni.
 * Œsophagostomum apiostomum.