DISEASES OF THE RECTUM AND ANUS.--The lower part of the alimentary canal is called the rectum, originally meaning straight. It is not straight in the human animal. It is six to eight inches long. The anus is the lower opening of the rectum. In health it is closed by the external Sphincter (closing muscle). Disease may wear this muscle out and then the anus remains open, causing the contents of the bowel to move involuntary. CONSTIPATION. Causes.--1. Mechanical obstruction. 2. Defective motion of the bowels. 3. Deficient bowel secretions. 4. Other causes. Mechanical obstruction.--Anything that will hinder the free and easy passage of the feces (bowel contents). Too tight external sphincter (rectum) muscle, stricture, tumors, etc. Bending of the womb on the bowel. Defective Worm-like Bowel Movement.--Irregular habits of living head the list causing this defective action. Everyone should promptly attend to Nature's call. Some people wait until the desire for stool has all gone, and in that way the "habit" of the bowels is gradually lost. Everyone should go to stool at a certain regular time each day, and at any other time when Nature calls. If a person heeds this call of Nature, the call will come regularly at the proper time, say every morning after breakfast. If these sensations (Nature's calls) are ignored day after day, the mucous membrane soon loses its sensitiveness and the muscular coat its tonicity, and as a result, large quantities of fecal matter may accumulate in the sigmoid (part of the bowel) or in the rectum without exciting the least desire to empty the bowels. Again, irregular time for eating and improper diet are liable to diminish this action also. Foods that contain very little liquid and those that do not leave much residue are liable to accumulate in the bowel and at the same time press upon the rectum hard enough to produce a partial paralysis. Deficiency of the Secretions.--Many of the causes that hinder worm-like motion are also likely to lessen the normal secretions of the bowel. Some kinds of liver diseases tend to lessen the secretions of the bowel, because the amount of bile emptied into the bowel is lessened. Sometimes the glands of the intestine are rendered less active by disease and other causes. Sundry Causes.--Diabetes, melancholy, insanity, old age, paralysis, lead poisoning and some troubles of local origin, like fissure of the rectum, ulceration, stricture and polypus. [DIGESTIVE ORGANS 137]