This is an extremely interesting and important anatomical structure, which, though, known to science for three hundred and fifty years, has received almost no attention until very recently. The ileocecal valve was discovered by Servius in 1563, A. D. It has been described by numerous anatomists, but was until recently regarded rather as an anatomical curiosity with no very important function.
The ileocecal valve consists of two parts - a sphincter muscle and a two-lipped check valve. The sphincter is formed by a thickening of the circular muscular fibres of the small intestine at its junction with the colon. The check valve is formed by an invagination of the small intestine into the colon. Something of an idea of the structure of the valve may be formed from the illustration opposite page 142.
*"Recent observations of Cannon have clearly demonstrated that the ileocecal sphincter acts in a manner very similar to the pylorus, retaining the foodstuffs in the small intestine until the digestive.
*The paragraphs in quotation marks are extracts from a paper by the author entitled. "Incompetency of the Ileocecal valve." work of the mid-gut is complete and the digested foodstuffs have been absorbed.
"Within the last few years Holzknecht, Schwartz, Groedel, Case, and numerous other roentgenologists have clearly demonstrated the functional activity of the ileocecal valve in controlling the movements of foodstuffs from the small intestine into the colon. These observations establish the necessity of the ileocecal valve for the following purposes:
"1. To hold back the digesting material in the small intestine until the digested portion has been transformed by the several digestive juices, and absorbed.
"2. To pass the mixture of unusable food residues, mucous, bile, and other excretions from the small intestine into the colon in small successive doses, so as to give the colon, the chief function of Which is the absorption of water and the discharge of unusable food residues and excreta, an opportunity to deal with the successive portions of material brought to it without being over-loaded.
"3. To prevent a reflux of material from the colon into the small intestine, which is accomplished by co-operation of the muscular sphincter of the proximal side, and the mechanical action of the membranous folds on the distal side of the ileocolic junction. The importance of this function of the ileocecal valve is greatly emphasized by the demonstration, by Cannon, Schwartz, Case, and others, of the existence of an anti-peristaltic action in the proximal half of the colon. Cannon gives a most graphic description of very powerful anti-peristaltic waves (as seen in the cat) beginning at about the middle of the transverse colon and passing rapidly backward along the colon to the cecum, compress-ing the liquid contents of the cecum so strongly as to cause a backward rush through the advancing ring of constriction. Case has confirmed these observations in the human subject in many cases."
There is perhaps no important bodily function so much neglected, and with such damaging results, as defecation or bowel movement. This function is too often looked upon as a humiliating act that must be secreted and avoided whenever possible, and that may properly be postponed to suit the exigencies of business or pleasure. The "call" of Nature for evacuation of the bowels is habitually ignored or resisted by children and adults alike, until it can no longer be suppressed, or until it disappears.
This wrong attitude toward one of the most important functions of the body is in large part responsible for the almost universal existence of constipation among civilized people, and of widespread and most appalling evil consequences, as we shall make clear in a subsequent chapter.
Ignorance of physiology, and especially of the physiology of digestion and nutrition, is doubtless the cause of this widespread evil. It is the duty of every physician and every trained nurse to do all possible toward the enlightenment of the chronically sick with whom they come in contact in relation to the absolute necessity for frequent and complete bowel action.
This is a subject which is too commonly tabooed by a false modesty that is entirely out of place.
Mothers and school teachers especially should give the matter special consideration. They should make sure that each child under their supervision has formed and maintains correct and regular habits in relation to evacuation of the bowels.
Until very recent times the process by which the colon discharges its contents was one of the most obscure in physiology. The discovery of the X-ray and of a method of examination by which the contents of the stomach and intestines could be made to cast a shadow on the fluorescent screen or upon a photographic plate, has thrown a flood of light upon this extremely interesting and practical question.
As already remarked, the process of defecation involves seven distinct acts. Three of these are under voluntary control, the other four being controlled by a special center known as the "center of defecation," located at the extreme lower end of the spinal cord.
The act of defecation is called forth by a sensation of fulness in the lower part of the colon. In a state of health we ordinarily perceive sensation only near the extremities of the alimentary canal. At the upper end of the food tube, guarding the entrance to the esophagus, there is located a reflex that controls the intake of food and liquids.
There are nerves in the mucous membrane at the back of the throat that, when stimulated by the contact of foods or liquids, give rise to the swallowing movement in which the esophagus opens and food or liquid present in the throat is drawn in by a strong suction movement. The act of swallowing is impossible without the contact of something that may be swallowed.
At the other end of the food tube, within a few inches of the anus - that is, at the upper part of the rectum - are found nerves that, when stimulated by the contact of fecal matters, give rise to a peculiar sensatipn recognized as a warning that the bowel contents should be discharged from the body.