=What the Colon Is For.= It is well, then to have a fair understanding of the structure and purpose of our intestinal machinery. Contrary to general opinion, the intestines are not a dumping-ground but a digestive organ. After the food is partly digested in the stomach, it passes through a twenty-two foot tube (the small intestine) into a five-foot tube (the large intestine or colon) where digestion is completed, the nutriment is absorbed, and the waste matter is passed on and out through the rectum. As the food passes along the colon, pushed slowly ahead by the peristaltic wave, or rhythmic muscular contractions of the intestinal wall, it is seized upon by the four hundred varieties of friendly bacteria which inhabit the intestines of every healthy person, and is changed into a form which the body can assimilate. Digestion in the stomach and small intestine is carried on by means of certain digestive juices, but in the large intestine it is the bacteria which do the work. Without them we could not live. Around the colon is a thick network of little blood vessels, all of which lead straight to the liver, the storehouse of the body. After the food is fully digested, it is passed through the thin intestinal wall into these tiny vessels and carried away to liver and muscles for storage or for immediate use. This process of absorption is carried on throughout the whole length of the colon. Not until the very end of the intestine is reached is all the nutrition abstracted. The bowel-content can properly be called waste matter only after it has reached the rectum or pouch at the lower end of the colon. Even then, this waste matter is not poison, but merely indigestible material which the body cannot handle. =Food, not Poison.= The colon is not a cesspool but a digestive and assimilating organ. Its content is not poison but food. Active elimination is important not so much because delay causes autointoxication or poisoning as because too large a mass is hard to manage and irritates the intestinal wall. The problem is not so much one of toxicology as of simple mechanics. If Nature had put within the body five feet of tubing which could easily become a cesspool and a breeder of poison, it is not at all likely that she would have laid alongside an elaborate system of blood vessels leading not out to the kidneys but into the storehouse of the liver; and if civilized man's changed manner of living had so upset Nature's plans as easily to transform his internal machinery into a chronic source of danger, we may be sure that he would long ago have gone the way of the unfit and succumbed to his own poisons.