THE MOVEMENTS OF THE INTESTINES STUDIED BY MEANS OF THE RÖNTGEN RAYS[33]
By W. B. Cannon
From the Laboratory of Physiology in the Harvard Medical School
Extracts from American Journal of Physiology, 1902
Introduction
The investigation of intestinal movements has been beset by the same difficulties that characterised the investigation of the gastric mechanism. Pathological subjects or animals subjected to the disturbing action of drugs and anæsthetics and of serious operations have been the only sources of our knowledge. A considerable difference of opinion as to the nature of the normal movements in the intestines has resulted from observations made under these necessary abnormal conditions. The slowly advancing peristaltic wave and the Pendelbewegung, or swaying movement, described by Ludwig, have been regarded as true physiological processes. Concerning antiperistalsis and the swiftly running vermicular contraction, observers are not so nearly in agreement. The activity of the large intestine has been described as simply peristalsis of a slower rate than that seen in the small intestine.
The best known of the intestinal movements is the normal peristaltic wave. This wave is slow, having a rate of about two centimetres per minute, is regular, and by most observers is said to move always in one direction. The progress of the contraction, as suggested by Nothnagel’s experiments, and as clearly stated by Mall and by Bayliss and Starling, is dependent upon a local reflex. According to Mall, when an object stimulates the mucosa there occurs above the point of stimulation a constriction which forces the object downward; and as it moves downward new regions immediately above the mass are by this reflex brought into constriction, and thus the wave and its stimulus advance together. “At the same time,” Mall states, “a sucking force, due to active dilatation below the body, may have a tendency to drag it down.” In what manner an active dilatation of the intestinal wall may occur so as to produce a “sucking force” he does not make wholly clear. Bayliss and Starling, in describing normal peristalsis in the intestine, state that the contractions above the bolus increase until there is a strong tonic constriction. This passes the bolus onward, and as it advances the ring of constriction follows it. While the bolus is passing down, the gut above it is traversed by waves running as far as the constricted ring. These observers state the law of intestinal peristalsis thus: “Local stimulation of the gut produces excitation above and inhibition below the excited spot.”
The pendulum movements are characterised by a gentle swaying motion of the coils, and are accompanied by rhythmical contractions of the intestinal wall. They continue with undiminished force after paralysis of the local nervous mechanism by nicotine or cocaine; they have been called, therefore, myogenic or myodromic contractions. Observers have described them variously as shortenings and narrowings of the gut, rhythmically repeated at nearly the same intestinal circumference; as alternating to-and-fro movements of the long axis without changes in the lumen; as local or extensive periodic contractions and relaxations mainly of the circular musculature; and as waves involving both muscular coats of the intestine, and travelling normally from above downward at a rapid rate (2 to 5 cm. per second). They have been seen in the dog, and in the rabbit and cat. In the cat Bayliss and Starling noticed that when the lumen of the gut was distended by a rubber balloon, there appeared rhythmical contractions, which nearly always were most marked at about the middle of the balloon; i. e., the region of greatest tension. This form of constriction, which, as my observation shows, is an indication of the manner in which the rhythmical contraction acts in the cat’s intestine, Bayliss and Starling seem to have regarded with slight attention, since it did not accord with the law of peristalsis.
The swift vermicular wave may pass the whole length of the intestine in about a minute. It is often seen just after death, as well as in pathological states such as intestinal anæmia or hyperæmia, and when the bowel contains gases and organic acids from decomposing food. Starling is inclined to regard this type of intestinal activity as an exaggeration of the rhythmic type; Mall, on the other hand, places it in a class by itself, and declares that its service is to rid the intestine rapidly of irritating substances. Nothnagel, who designates this form of movement with the term Rollbewegung, thinks it is transitional between a physiological and a pathological activity.
The existence of antiperistalsis has been so much questioned that it will be considered in a special section of this paper, where my observations may be conveniently introduced.
The common understanding of the manner in which food passes through the intestinal canal is that the chyme ejected from the stomach is pressed downward by a peristalsis, which passes slowly over a part or all of the small intestine. The peristaltic waves of the colon are supposed to constitute an independent group, similar to those of the small intestine, but weaker and slower. Movements of the food other than the uninterrupted advance have been mentioned by some observers. Starling states that the effect of the pendulum movement is to mix the contents of the intestine and bring them into intimate contact with the mucous membrane. Grützner writes that he has been brought “by strange and peculiar observations” to believe that the fluid contents of the small intestine move irregularly forward, then forward and back, then perhaps remain quiet for some time, only to pass backward for a long distance, and finally to move forward steadily to the end. In this manner the food is mixed and brought into contact with the absorbing walls. The to-and-fro shiftings of the food Grützner ascribed to advancing and retrograde contractions of the intestinal musculature, and he argued that even circular constrictions must force the liquid contents away in both directions. To support his contention, Grützner introduced mercury into the intestine and observed it with the Röntgen rays. After noting a backward and forward movement of the mercury he dismissed the method, saying, “Many a flash must come from the Röntgen tube before the normal movement of the intestinal contents is made entirely clear by this method.”
The following account is a summary of many repeated observations on different animals, and is a contribution to a clear understanding of the normal movements of the intestines and their contents.