732 



PHYSIOLOGY OF DIGESTION AND SECRETION. 



contractions somewhat similar to the rhythmic segmentations in 

 the small intestine.* These movements (haustral churning) 

 would seem to favor also the processes of absorption. Hertz 



Trunk 



Kami Efferent 



Conation mesenfer/eum infer/us 

 Branches to C, 



Fig. 287. Schema to show the innervation of the rectum and internal sphincter 

 of the anus, and the formation of the hypogastric plexus. (After Frankl-Hochwart and 

 Frohlich.) 



estimates that in man the food requires about 2 hours to pass 

 from the ileocecal valve to the hepatic flexure and about 4^ 

 hours to reach the splenic flexure. As the colon becomes filled 

 some of the material penetrates into the descending part, where 

 the normal peristalsis carries it very slowly toward the rectum. 



The large intestine particularly the descending colon and 

 rectum receives its nerve supply from two sources (Fig. 287): 

 (1) Fibers which leave the spinal cord in the lumbar nerves 

 (second to fifth in cat), pass to .the sympathetic chain, and 

 thence to the inferior mesenteric ganglia, which probably form 

 the termination of the preganglionic fibers. From this point 

 the path is continued by fibers running in the hypogastric nerves 

 and plexus. Stimulation of these fibers has given different 

 results in the hands of various observers, but the most recent 

 workf indicates that they are inhibitory. (2) Fibers that leave 



* Elliott and Barclay-Smith, "Journal of Physiology," 31, 272, 1904. 



f Langley and Anderson, "Journal of Physiology," 18, 67, 1895. Bay- 

 liss and Starling, ibid., 26, 107, 1900. Also Wischnewsky, in Hermann's 

 "Jahresbericht der Physiologic," vol. xii., 1895. 



