The increased flow of blood to the mucous membrane of the colon furthers this extraordinary secretion by the glands. As has been pointed out, inflammation, septic poisoning, intestinal foulness, or retained feces, act as irritants on the mucous membranes, thereby drawing the blood to the colon where it is excreted and exhaustion follows. The great danger in diarrhea, therefore, is the rapid depletion of the vital force. But when the small intestines are affected the consequences may be still more deplorable. Then the unassimilated food is hurried along too quickly for absorption and the body receives but little nourishment to restore its powers. Thus another draught is made upon the sufferer's reservoir of vitality, and hence additional exhaustion. But this waste of tissue, loss of vital force, non-assimilation and non-supply, are not so grave as the positive danger of the permanent destruction of the millions of small absorbing vessels (villi) of the small intestine by a continuance of this abnormal irritation. Of course the secretory and excretory glands of the colon also suffer, and we then have costiveness resulting from lack of absorption and excretion. Abnormal irritability of the bowels is necessarily involved in the inflammatory process known as proctitis and colitis. Increase this irritability to a certain point and diarrhea takes the place of constipation--a much more alarming symptom. Diarrhea is more alarming because the intensified local activity of the excretory glands of the bowels brings on, as has been said, a general exhaustion of the vital powers. The severity of diarrheal symptoms is much increased by the character and abundance of bacterial poisons. Bacteria find a ready medium in fetid feces, and are absorbed by the excited glands to the degree in which these glands have time and power for absorption. Of course the extent and character of the intestinal irritation have a good deal to do with the severity of the diarrheal symptoms. This irritation is not infrequently intensified by a catarrhal process, or by a lesion of an ulcerative nature. All these forms of irritation bring on "excessive intestinal peristalsis"--which, accordingly, is our definition of diarrhea. The normal peristaltic action of the intestines propels the nutritive as well as the effete material through the canal at a rate that allows of both proper absorption and timely elimination. But when excessive peristalsis occurs, neither absorption nor elimination will be normal or suited to the requirements of the system.