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PHYSIOLOGY OF DIGESTION AND SECRETION. 



former receive their extrinsic motor fibers mainly if not entirely 

 through the vagus (bulbar autonomic) , while the latter receive their 



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GpnolioH ineseMt&ricum wferj 

 Branches (a Cole 



MLganql. 

 IV.L. 



V.L 



VI. L 

 Vl.h.gangl. 



vn.L. 



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 1. 2ocrol 



M.S. 



Pkxi^ ffyfac^sli-iciis 



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

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

 Frshlich.) 



motor fibers mainly, if not entirely, through the pelvic nerve 

 (sacral autonomics), arising near the extreme lower end of the cord. 

 The small intestine receives its inhibitory fibers through the 

 splanchnic nerve and superior mesenteric ganglion (thoracic 

 autonomics), while the colon and rectum get their inhibitory fibers 

 through splanchnic branches that connect with the inferior mesen- 

 teric ganghon (thoracic autonomics). 



Defecation. — The undigested and indigestible parts of the 

 food, together with some of the debris and secretions from the 

 alimentary tract eventually reach the pelvic colon and rectum. 

 Authorities differ as to whether the rectum normally contains 

 fecal material or not. According to observations made upon man 

 by means of a:;-rays fecal material is normally absent from the 

 rectum except just before defecation. It seems probable that a 

 distinct desire to defecate is felt only when the feces have actually 

 entered the rectum and produced some distention. The fecal 

 material is retained within the rectum by the action of the two 

 sphincter muscles which close the anal opening. One of these 

 muscles, the internal sphincter, is a strong band of the circular 



