SECTION IX 

 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 movements of the gut, it is neces- 

 sary to exclude the disturbing influences due to reflexes through the central 

 nervous system either by extirpation 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 about 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 ' enterograph ') it is possible 

 without opening the gut to record the movements 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 con- 

 tracting synchronously. When the contractions are recorded by means of a 

 balloon, the constriction which accompanies each contraction is seen to 

 be most marked at the middle of the balloon, i.e. at the point of greatest 

 tension, and the amplitude of the contractions is augmented by increasing 

 the tension on the walls of the gut. These movements are unaffected by 

 the direct application of drugs such as nicotine or cocaine, which we might 



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