MOVEMENTS OF THE ALIMENTARY CANAL, ETC. 321 



tine of living animals when stimulated artificially, and Grutzner l reports a 

 number of curious experiments which seem to show that substances such as 

 hairs, animal charcoal, etc., introduced into the rectum may travel upward to the 

 stomach under certain conditions. The peristaltic wave normally passes down- 

 ward, and that this direction of movement is dependent upon some definite 

 arrangement in the intestinal walls is beautifully shown by the experiments of 

 Mall 2 and others upon reversal of the intestines. In these experiments a por- 

 tion of the small intestine was resected, turned round and sutured in place 

 again, so that in this piece what was the lower end became the upper end. 

 In those animals that made a good operative recovery the nutritive condition 

 gradually became very serious, and in the animals killed and examined the 

 autopsy showed accumulation of material at the upper end of the reversed 

 piece of intestine, and great dilatation. 



The peristaltic movements of the intestines may be observed upon living 

 animals when the abdomen is opened. If the operation is made in the air 

 and the intestines are exposed to its influence, or if the conditions of tempera- 

 ture and circulation are otherwise disturbed, the movements observed are 

 often violent and irregular. The peristalsis runs rapidly along the intes- 

 tines and may pass over the whole length in about a minute ; at the same time 

 the contraction of the longitudinal muscles gives the bowels a peculiar writhing 

 movement. Movements of this kind are evidently abnormal, and only occur 

 in the body under the strong stimulation of pathological conditions. Normal 

 peristalsis, the object of which is to move the food slowly along the alimentary 

 tract, is quite a different affair. Observers all agree that the wave of contraction 

 is gentle and progresses slowly. It has been studied very successfully, so far as 

 rate of movement is concerned, by experiments upon animals in which a loop 

 of the intestines was resected, to make a " Thiry-Vella " fistula (see p. 246). 

 Cash 3 finds that in such isolated loops foreign substances introduced are pro- 

 pelled at different rates according to the condition of the animal. In the fast- 

 ing animal it requires from one and a half to two and a half minutes for a 

 distance of one centimeter. During exercise the movement is more rapid, 

 while during the first few hours of digestion, that is the time during which 

 the stomach is emptying its contents into the intestine, the velocity of the 

 movement is greatly increased, requiring only from twenty to fifty seconds to 

 cover a distance of one centimeter. The force of the contraction as measured 

 by Cash in the dog's intestine is very small. A weight of five to eight grams 

 was sufficient to check the onward movement of the substance in the intestine 

 and to set up violent colicky contractions which caused the animal evident 

 uneasiness. We may suppose that under normal conditions each contraction 

 of the antrum pylori of the stomach, which ejects chyme into the duodenum, 

 is followed by a peristalsis that beginning at the duodenum passes slowly 

 downward for a part or all of the small intestine. According to most 



1 Deutsche medicinische Wochenschrift, 1894, No. 48. 



2 The Johns Hopkins Hospital Reports, vol. i. p. 93. 



3 Proceedings of the Royal Society, London, 1887, vol. 41. 

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