210 



DIGESTION 



roots. According to Fellner, the sacral nerves are motor for the rectal 

 longitudinal muscle fibers, and inhibitory for the circular fibers, while 

 the hypogastric influence is contractile for the circular fibers and relaxa- 

 tive to the longitudinal fibers (the so-called " crossed innervation"). 

 Winkler claims that the hypogastric is the proper motor nerve of the 

 whole large intestine. The vagus is probably both motor and inhibitory. 

 THE MOVEMENTS OF THE LARGE INTESTINE are less complicated 

 than are those of the small gut. According to Cannon, the chief move- 

 ment of the descending colon is the very slow peristalsis produced by 

 the progressive tonic contraction of the circular fibers. In the remainder 

 of the large gut, in man the ascending and transverse colon and the 

 cecum, the chief movement and themost common one is anti peristalsis. 



FIG. 109 



FIG. 110 



The ileo-cecal valve as seen on cutting away 

 a part of the cecum: 1, ileum; 2, cecum; 3, 

 ascending colon; 4, vermiform appendix; 5, 

 opening into the same; 6, inferior lip; 7, superior 

 lip; 8, aperture of the valve; 9, its retinaculum. 

 Y 2 . (Rauber.) 



Cells of a frog's liver (injected with sodium 

 eulphindigo'tate), to show how the bile-channels 

 begin. (Kupffer.) 



The result of this backward per- 

 istaltic movement is to keep the 

 liquid chyle, coming continually 

 into the colon from the ileum, a 

 long time in the cecum and to pre- 

 vent its being pushed onward 

 into the rectum before absorp- 

 tion of its liquid has had time to take place. Each period of anti- 

 peristalsis (in the cat) lasts from two to eight minutes, and the periods 

 recur at intervals of from ten to twenty minutes. Rhythmic pulsating 

 or segmenting movements are of rare occurrence in the large gut of the 

 cat, but were seen once or twice; tonic constrictions seem to occur at 

 intervals along the colon when the latter is filled, and these tend to press 

 the contents toward the rectum. Bayliss and Starling corroborate 

 Cannon's observation that it is the distention of the colon with chyle 

 that actuates the movements of the tube. 



