MOVEMENTS OF THE SMALL INTESTINE. 255 



small intestine is necessary to proper digestion and even essential to life, and 

 although the variations in the flow of bile with digestion are now well estab- 

 lished, physiologists have but little definite information concerning the exact 

 mode of action of the bile in intestinal digestion and absorption. Nearly all 

 that can be said on this subject is that the action of the bile seems to be 

 auxiliary to that of the other digestive fluids. 



MOVEMENTS OF THE SMALL INTESTINE. 



By the contractions of the muscular coat of the small intestine, the ali- 

 mentary mass is made to pass along the canal, sometimes in one direction and 

 sometimes in another, the general tendency, however, being toward the cae- 

 cum ; and the partially digested matters which pass out at the pylorus are pre- 

 vented from returning to the stomach by the peculiar arrangement of the 

 fibres which constitute the pyloric muscle. Once in the intestine, the food is 

 propelled along the canal by peculiar movements which have been called peri- 

 staltic, when the direction is toward the large intestine, and antiperistaltic, 

 when the direction is reversed. These movements are of the character pecul- 

 iar to the non-striated muscular fibres ; viz., slow and gradual, the contraction 

 enduring for a certain time and being followed by a correspondingly slow and 

 gradual relaxation. Both the circular and the longitudinal muscular layers 

 participate in these movements. 



Although the mechanism of the peristaltic movements of the intestine 

 may be studied in living animals after opening the abdomen or in animals 

 just killed, the movements thus observed do not entirely correspond with 

 those which take place under natural conditions. In vivisections no move- 

 ments are observed at first, but soon after exposure of the parts nearly the 

 whole intestine moves like a mass of worms. In the normal process of diges- 

 tion the movements are never so general or so active. They take place more 

 regularly and consecutively in those portions in which the contents are most 

 abundant, and the movements are generally intermittent, being interrupted 

 by long intervals of repose. In Busch's case of intestinal fistula, there existed 

 a large ventral hernia, the coverings of which were so thin that the peristal- 

 tic movements could be readily observed. In this case the general character 

 of the movements corresponded with what has been observed in the inferior 

 animals. It was noted that the movements were not continuous, and that 

 there were often intervals of rest for more than a quarter of an hour. It was 

 also observed that the movements, as indicated by flow of matters from the 

 upper end of the intestine, were intermitted with considerable regularity dur- 

 ing part of the night. Antiperistaltic movements, producing discharge of 

 matters which had been introduced into the lower portion of the intestine, 

 were frequently observed. 



As far as has been ascertained by observations upon the human subject 

 and warm-blooded animals, the regular intestinal movements are excited by 

 the passage of alimentary matters from the stomach through the tube during 

 the natural process of digestion. By a very slow and gradual action of the 

 muscular coat of the intestine, its contents are passed along, occasionally the 



