MOVEMENTS OF THE ALIMENTARY CANAL, ETC 383 



would be to push onward the contents of the intestines in the direction of the 

 movement. It is obvious that the circular layer of muscles is chiefly involved in 

 peristalsis, since constriction can only be produced by contraction of this layer. 

 To what extent the longitudinal muscles enter into the movement is not definitel v 

 determined. The term " anti-peristalsis" is used to describe the same form of 

 movement running in the opposite direction — that is, toward the stomach. 

 Anti-peristalsis is usually said not to occur under normal conditions; it has 

 been observed sometimes in isolated pieces of intestine or in the exposed intes- 

 tine of living animals when stimulated artificially, and Griitzner 1 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 Mas 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 onlv 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. According to Bayliss and Starling, 3 the 

 peristaltic movement is a complicated reflex through the intrinsic ganglia. 

 When the intestine is stimulated by a bolus placed within its cavity, the 

 musculature above the point stimulated is excited, while that below is in- 

 hibited. In accordance with this law they find that in peristalsis the advanc- 

 ing wave of constriction is preceded by a wave of relaxation or inhibition. 

 The force of the contraction as measured by Cash ' in the dog's intestine is 

 very small. A weighl of five to eight grains was sufficient to check the on- 

 ward movement of the substance in the intestine and to set up violent colicky 



1 Deutsche medicinische Wpchenschrift, 1894, No. 18. 



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

 8 Journal of Physiology, L899, vol xxiv. p. 99. 



4 Proceedings of tin- Royal Society, London, 1887, vol. 41. 



