In 1894 Grützner published an observation and made an assumption about which there has since been much controversy. He maintained that when normal salt solution, holding in suspension hair, powdered charcoal, or starch grains, is injected into the rectum, it is carried upward into the small intestine and may even enter the stomach. These experiments have been repeated by several observers. Some have confirmed Grützner’s results; others have failed, after using most careful methods, to find any evidence of the passage of the injected material back to the stomach, and they have declared that the apparent success was due to carelessly allowing the food of the animal to become contaminated with the test materials, so that these were introduced into the stomach by way of the mouth. That antiperistalsis does not occur in the small intestine seems to be proved by Mall’s experiment of reversing a portion, sewing it in place, and then finding that the food does not pass the reversed region, but collects at the upper end. Sabbatani and Fasola reversed stretches of small intestine of varying length, and found that the reversed portions allowed fluids to pass, but that the persistence of the physiological direction of movement caused an accumulation of undigested food in the region of the upper suture. However a portion of the intestine lay in relation to the rest, it always manifested the normal peristalsis. Many other observers working directly on the intestine confirm this testimony and state that the progress of the constriction-rings is always downward, and that antiperistalsis is not physiological. In 1898, however, Grützner took his stand again in favour of a backward movement in the intestines, and in a somewhat metaphysical manner argued that peristalsis and antiperistalsis belong to each other just as relaxation of muscle is related to contraction. He assumed that as the contents are advanced by slow peristalsis, so are they returned by a similar movement in the opposite direction, and he mentions several pathological cases (fistula of intestine) to substantiate the assumption.
By means of the X-rays it is possible to see just what takes place when a fluid is injected into the rectum. For the purpose of determining how nutrient enemata are received and acted upon in the intestines, I have introduced thin, fluid masses in large and small amounts, and thick, mushy masses in large and small amounts, in different animals. The enemata consisted of 100 c.c. of milk, one egg, ten to fifteen grams of bismuth subnitrate, and two grams of starch to hold the bismuth powder in suspension. To make the thick enema all these were stirred together and boiled to a soft mush; to make the thin enema all the parts were boiled together except the egg, which was added after the boiled portion was cooled. The small amount injected was 25 c.c.; the large amount almost 90 c.c., about the capacity of the large intestine when removed from the body. The animals were given first a cleansing injection, and after this was effective the nutrient material was introduced. In order to make sure of the observation, a control radiograph was first taken to show no bismuth food present, and other radiographs taken at varying intervals after the injection to record the course the food was following.
Figure 9.—- Radiographs showing that after a large nutrient enema (about 90 c.c.) has been given the food is forced more and more from the large into the small intestine. The enema was introduced at about 1.40 P.M. At 3.00 segmentation was occurring in many loops.
These experiments show that when small amounts of nutrient fluid are introduced they lie first in the descending colon. In every instance antiperistaltic waves are set going by the injection, and the material is thereby carried to the cæcum. When large amounts are injected they stop for a moment in the region between the transverse and descending colon, as if a constriction existed there. Then a considerable amount of the fluid passes the point, and antiperistaltic waves carry it to the cæcum. In any case the repeated passing of the waves seems to have the effect of promoting absorption, for in the region where these waves continue running, the shadows become gradually more dim, and finally the bismuth appears to be only on the intestinal walls; in other regions, e. g. in the descending colon, the shadows retain their original intensity. Small injections have never in my experience been forced even in part into the small intestine; but with the larger amounts, whether fluid or mushy, the radiographs show many coils of the small intestine containing the bismuth food.
The passage of the injected material beyond the ileocæcal valve is probably due entirely to antiperistalsis in the colon,—a factor unknown to both Grützner and his opponents. The valve, which is thoroughly competent for food coming normally from the small intestine into the large, is curiously incompetent for a substance, even of the consistency of thick cream, introduced in large amount by rectum. When the valve first permits the food to enter the ileum, the fluid pours through and appears suddenly as a winding mass occupying several loops of the intestine (Fig. 9, 1.50, about ten minutes after the injection). The mass is continuous from the valve to the other end; antiperistalsis is therefore not visible in the small intestine under the circumstances of this experiment. The antiperistaltic waves of the colon, however, continue running; the transverse and ascending colon are thus almost emptied, and the small intestine more and more filled with food (Fig. 9, 2.15 and 3.00). After a short time the typical segmenting movements can be seen in the loops, busily separating the food into small masses, and over and over again dividing and redividing them.
I have never seen food material pass back from the colon so far as the stomach; but once, about ten minutes after an injection of 100 c.c. of warm water, the cat retched and vomited a clear fluid resembling mixed water and mucus. In the fluid were two intestinal worms still alive.
The importance of the mechanism by which nutrient enemata are passed backward in the intestine is evident. In the colon the nutrient material is worked over by the antiperistaltic waves, intimately mixed with whatever digestive juices may be present, and exposed to the organs of absorption in that region. If the enemata are large, the digestive and absorptive processes are by no means confined to the colon, but may take place along extensive surfaces of the small intestine. I have repeatedly seen rhythmic segmentation active throughout many loops of the small intestine, thus exposing the injected food to the same mixing and absorbing processes as affect the nutriment which has come through the stomach in a normal manner.
The Effect of Emotions and Sleep
Observations on the stomach of the cat showed that the peristalsis is inhibited whenever the animal manifests signs of anxiety, rage, or distress. Since the extrinsic innervation of a large part of the intestinal tract is the same as that of the stomach, it is of interest to note the effect of emotional states on the movements of the intestines. Esselmont, in a study of the dog’s intestine, noted constantly after signs of emotion a marked increase of activity lasting for only a few moments. Fubini also observed that fear occasioned more rapid peristalsis. There is no doubt that many emotional states are a strong stimulus to peristalsis, but it is equally true that other emotional states inhibit peristalsis. In the cat the same conditions which stop the movements of the stomach stop also the movements of the intestines.