SECTION VIII 

 MOVEMENTS OF THE INTESTINES 



THE movements of the intestines can be investigated either by 

 observation of the exposed gut, or by the shadow method introduced 

 by Cannon, in which the nature of the movements is judged from 

 the shadows of food containing bismuth which are thrown on a 

 sensitive screen by means of the Rontgen rays. These movements 

 have been the subject of experimental investigation for many years, 

 but with varying results. The great discrepancy which obtained 

 between the statements of earlier observers is due to the fact that 

 they failed to exclude the many disturbing impulses which can play 

 on any segment of the gut, either reflexly through the central nervous 

 system, or from other parts of the alimentary canal itself through 

 the local nervous system. In order to observe the normal move- 

 ments of the gut, it is necessary to exclude the disturbing influences 

 due to reflexes through the central nervous system either by extir- 

 pation of the whole of the nerve plexuses in the abdomen, or by 

 division of the splanchnic nerves, or by destruction of the lower part 

 of the spinal cord from a'bout the middle dorsal region. If the 

 abdomen of an animal which has been treated in this way be opened 

 in a bath of warm normal salt solution, so as to exclude the disturbing 

 influence of drying and cooling of the gut, the small intestine will be 

 seen to present two kinds of movements. In the first place, all 

 the coils of gut undergo swaying movements from side to side 

 the so-called pendular movements. Careful observation of any coil 

 will show that these movements are attended with slight waves of 

 contraction passing rapidly over the surface. If a rubber balloon, 

 filled with air and connected with a tambour, be inserted into any 

 part of the gut, it will reveal the existence of rhythmic contractions 

 of the circular muscle repeated from twelve to thirteen times per 

 minute. By means of a special piece of apparatus (the ' entero- 

 graph ') it is possible without opening the gut to record the move- 

 ments of either circular or longitudinal muscular coats ; and it is 

 then found that both coats present rhythmic contractions at the same 

 rate, the two coats at any point contracting synchronously. When 

 the contractions are recorded by means of a balloon, the constriction 

 which accompanies each contraction is seen to be most marked at 



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