The peculiar yellowish-green secretion of the liver known as the bile appears not only to assist in the solution and digestion of the food, but to act as a natural antiseptic, which checks the too great multiplication of the various germs which are naturally always to be found in the intestine. It is comparatively rarely that the liver itself strikes work, but what does very commonly happen is that a chill, or a mechanical or chemical irritation of the bowel, may extend to the bile duct, and by causing swelling, or spasmodic action of its muscles, prevent the contents of the gall bladder, in which the bile secreted by the liver is stored up, from passing on into the intestine. The chill or irritant that thus stops the flow of the bile necessarily at the same time produces a greater or less amount of catarrh and inflammation of the lower bowel, which, lying as it does next to the wall of the abdomen, is most easily affected by cold; but stoppage of the flow of bile into the intestine seems an essential element in the production of dysentery, as a more or less complete absence of bile from the motions is a universal symptom of the condition, and to restore the action of the liver is, practically speaking, in cases taken sufficiently early, equivalent to curing the disease. As has been already noticed, dysentery may be caused by a variety of mechanical and chemical irritants, but by far the commonest cause is undoubtedly chill to the surface of the abdomen, and the reason the disease is so common in tropical climates is their peculiarly treacherous feature of the chill that precedes the dawn. The earlier part of the night is often intolerably close and sultry, and it is only with difficulty that the jaded European manages to get off to sleep, and then naturally with next to no covering of the body. As the hours pass, the temperature falls somewhat and he sleeps more easily and deeply, and when the peculiar chill falls that usually precedes a tropical dawn, he is too far off in the land of dreams to be roused by the cold; and the abdomen, bared probably by his restless movements during the earlier part of the night, is left exposed to the treacherous chill.