The food masses are moved along by rhythmic contractions of the intestine, and absorption goes on when the food has been so changed that it can soak through the intestinal walls into the blood and lymph vessels. The small intestine is about 20 feet long, and consequently affords a large surface for absorption, as does also the large intestine, into which the small intestine opens. The blood and lymph carry the digested food substances to all parts of the body, and thus the different tissues are provided with the materials they need for growth, repair, and energy. Excess of food substances may be stored as fat or expelled from the body. As the blood and lymph go through the tissues they take from the tissues the refuse, or the part that remains after the fuel substances have been consumed. This refuse from the tissues may be likened to the ashes from a furnace; it is finally eliminated from the body through the kidneys and lungs, and to some extent through the skin and bowels. The part of the food that is not digested of course never soaks through the intestinal walls; it merely passes through the small and large intestines and is finally expelled as feces or bowel movements. The characteristic odor of fecal matter results from the action of bacteria upon it while in the large intestine. It must be remembered that the body is not nourished merely by swallowing food: in order to nourish the body food must also be digested, absorbed, and made use of by the tissues. Many factors may operate both in health and in sickness to render food indigestible. It may be originally unsuited to the human digestive apparatus, or spoiled, or poor in quality, or badly cooked. But even when wholesome in itself it may be ill-adapted to a particular person at a particular time; thus it may be too great in amount, or eaten at improper hours. Moreover a person's own idiosyncrasy or manner of living or fatigue or illness may render it especially indigestible for him. Experiments have shown that pain, fear, worry, and other unpleasant emotions actually stop the action of the digestive juices and check muscular contractions of the small intestine. Furthermore, even the absence of pleasant anticipation of food has been shown to delay digestion for hours. Thus scientific knowledge confirms our common experience that such mental states seriously interfere with digestion. The converse is also true. Agreeable taste and odor of food, or even pleasurable thought of it, start the secretion of digestive fluids. It is a common saying that the mouth waters at the prospect of inviting food, but it is less well known that appetizing food does actually start the stomach juices also. A person who understands the physiological effect that the emotions have upon digestion is in a far better frame of mind to cope successfully with the difficulties of feeding the sick than one who considers sick persons' likes and dislikes entirely irrational. FEEDING THE SICK