No digestion goes on in the large intestine, the function being to dry by absorbing water. The _movements_ are practically the same as those of the small intestine except that they are much less active. Fermentation makes the contents acid. By the time food reaches the rectum it has been thoroughly digested and has given up its nourishment. It is then expelled as waste matter or _feces_. _Defecation_ combines the involuntary movements of peristalsis and relaxation of the sphincters with the voluntary aid of the abdominal muscles. The _ano-spinal reflex_, by which movements of the bowel are regulated, is in the lumbar enlargement of the cord. The _hemorrhoidal veins_ in the lower rectum are connected with both the systemic and the portal veins and have no valves so that, as they are subjected to much strain, they often become varicose and dilated. This condition is called _hemorrhoids_ or _piles_. _Obstruction_ of the intestine may be caused by the growth of a constricting band, by _intussusception_ or telescoping of the intestine on itself, especially at the ileo-cecal valve, or by _volvulus_ or twisting. _Foreign bodies_ are sometimes found in the appendix but they are not usually the cause of appendicitis. _Cancer of the intestine_ is common and its mass is apt to cause obstruction with all its attendant symptoms. It may necessitate an artificial anus. _Hernia_ or _rupture_ may also occur and the hernia may become strangulated. =Food and Metabolism.=--Anything serves as food that replaces or hinders the loss to which the component parts of the body are liable. Proteins, carbohydrates, fats, some mineral matters, as salt and perhaps iron, and water are needed. The energy once expended by plants or animals in the formation of the materials which serve as food is set free in the body by the breaking up of these complex substances into their original elements, which are then recombined into the complex materials needed for the body’s life and growth. This process of building up complex materials from simple ones is known as _anabolism_ and that of breaking them down as _katabolism_, while the two combined form the complete cycle of _metabolism_. Those foods have the best value that give up their energy most readily. For their combustion, heat, oxygen, and water are needed. Hunger indicates that the supply of material for katabolism has been used up and that more is needed, just as thirst indicates the need of the system for more fluids.