DIGESTION. 95 



designate the movements running in an exactly opposite direction: 

 that- is, toward the stomach. 



Pendular Movements. These are the very slight swinging to- 

 aml-i'ro oscillations, probably caused by the contractions of the longi- 

 tudinal fibers. 



Cannon has shown that in the cat, when fed, a portion of the 

 small intestine may be seen, with its continuous contents, to sud- 

 denly be divided into segments. These segments are then also sub- 

 divided. This segmentation of the intestinal contents does not move 

 the food along. A peristaltic wave does that. These movements incor- 

 porate the food with the ferments. When a peristaltic wave reaches 

 the ileo-colic sphincter, it relaxes and permits the intestinal con- 

 tents to pass into the colon. If a reflux wave of the colon takes 

 place, it contracts, when the proximal part of the colon is distended - 

 Then contractions, an antiperistaltic wave, travel from the point of 

 union of the ascending and transverse colon towards the caecum. 

 Then peristaltic waves drive the contents into the distal colon. 



In the large intestine, the distal part of the colon and its 

 adjacent sigmoid flexure are a resting place for the faeces, and are 

 concerned in defecation. The chief point about the distal colon is 

 its complete subordination to the spinal cord. The ileo-colon, the 

 transverse colon, and the descending colon are a place for the pro- 

 pulsive peristalsis, as the descending colon is never distended. 



NERVE=SUPPLY OF THE INTESTINES. 



The small intestine receives fibers from the greater and smaller 

 splanchnic nerves, which pass through the semilunar and superior 

 mesenteric ganglia, and then pass along the mesenteric arteries to 

 their destination. The right vagus also supplies the intestine with 

 fibers. 



The sympathetic ganglia of Auerbach lie between the two mus- 

 cular coats and extend from the oesophagus down throughout the 

 small and large intestine. Meissner's ganglia, also belonging to the 

 sympathetic system, lie in the submucous coat. The vagi convey 

 motor impulses to the intestine, while the sympathetics mainly con- 

 vey inhibitory, although they also carry motor, impulses. Slight 

 stimulation of the splanchnic calls out motion, strong stimulation 

 inhibition of the intestinal movements. I have found that, when 

 the right vagus is divided in a rabbit and the cardio-inhibitory fibers 

 are allowed to degenerate for five days, electric stimulation of the cut 

 vagus slows the pendular movement. 



