Motility of the Small Intestine

ALTHOUGH the dynamic state of the intestinal musculature was well appreciated by Bayliss and Starling at the end of the last century, subsequent progress in our understanding of the mechanisms controlling intestinal motility has been disappoifitingly slow. Progress has been delayed by a confused nomenclature. The terms 'motility', ' peristalsis' and 'tone' are often used indiscriminately and without precise definition. For example, the term ' motility' is used to describe a variety of different features of the intestinal movements, including the rate of passage of food and other materials along the alimentary tract, the appearances of the gut on direct observation or at fluoroscopy, the 'tone ' or rigidity of the bowel wall and the pressures developed in the lumen of the bowel. The result is that references to bowel movements in clinical writings are frequently so vague and imprecise as to be, at times, meaningless. Progress in this field of study has also been hindered by difficulties in methodology. Patients and subjects always dislike swallowing tubes and as it has until recently been necessary to pass a tube into the small intestine to obtain information about bowel movements, there has been a natural reluctance on the part of clinical physiologists to subject their patients to this discomfort. Furthermore, the nausea and distress caused by the presence of a tube in the alimentary tract may vitiate studies using these methods. The advent of the ingestible telemetering capsule, however, has for the first time made it possible to obtain quantitative data from the alimentary tract without the use of tubes and it seems likely that the prototypes undergoing development at present herald a new era in the study of gastrointestinal function. It is therefore an appropriate time to examine existing knowledge about the motility of the small intestine in man.