738 



PHYSIOLOGY OF DIGESTION AND SECRETION. 



would seem to favor also the processes of absorption. Hertz 

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

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

 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 receives its nerve supply from two sources 

 (Fig. 287) : (1) Fibers which leave the spinal cord in the lumbar 



Ganglion mesenferieum uiftriui 

 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 

 Frehlich.) 



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 general view * is that they 

 are inhibitory. (2) Fibers that leave the cord in the sacral nerves 

 (second to fourth) form part of the nervi erigentes or pelvic nerves 

 and enter into the hypogastric plexus. When stimulated these 

 fibers cause contractions of the muscular coats; they may be re- 



* Langley and Anderson, "Journal of Physiology," 18, 67, 1895. Bayliss 

 and Starling, ibid., 26, 107, 1900: Gaskell, "The Involuntary Nervous System," 

 1916. 



