MOVEMENTS OF THE ALIMENTARY CANAL. 727 



and the pylorus. There is a certain orderliness in the movements 

 of the stomach, and especially in the separation and ejection of the 

 more liquid from the solid parts, which shows the existence of a 

 specially adapted mechanism. These movements have been studied 

 by many investigators, making use of various experimental meth- 

 ods. The first noteworthy contributions to this subject were 

 those made in this country by Beaumont in his famous observations 

 upon Alexis St. Martin, the Canadian voyageur, who had a per- 

 manent fistulous opening in his stomach as the result of a gunshot 

 wound.* In recent years the subject has been studied with great 

 success by means of the x-rays, f on the excised stomach, J and by 

 means of tambours or sounds introduced into the stomach to 

 measure the pressure changes. These researches all unite in em- 

 phasizing one fundamental point namely, that the fundic end 

 of the stomach is not actively concerned in these movements, but 

 serves rather as a reservoir for retaining the bulk of the food, while 

 the muscular pyloric region is the apparatus which triturates and 

 macerates the food and forces it out from time to time into the 

 duodenum. According to the observations made with the z-ray 

 apparatus, movements begin a few minutes after the entrance of 

 food into the stomach. Small contractions start in the middle 

 region of the stomach and run toward the pylorus. These moving 

 waves of contraction appear at regular intervals. The pyloric 

 portion becomes lengthened and it may be noticed that in this 

 region the peristaltic waves become more and more forcible as 

 digestion progresses. These running waves or rings of contraction 

 serve to press the stomach contents against the pylorus. According 

 to Cannon, they occur in the cat at intervals of 10 seconds and each 

 wave requires about 20 seconds to reach the pylorus. While in 

 human beings, to judge from the sounds which may be heard upon 

 ausculation when food mixed with air is given, they occur at intervals 

 of about 20 seconds. The obvious result of these movements is to 

 mix the food thoroughly, in the intermediate and pyloric portions 

 of the stomach, with the acid gastric juice and to reduce it to a thin, 

 liquid mass, the chyme. At certain intervals the pyloric sphincter 

 relaxes and the contraction wave squeezes some of the fluid con- 

 tents into the duodenum with considerable force. The mechanism 

 controlling the relaxation of this sphincter is obscure. It does not 

 occur with the approach of each contraction wave, but at irregular 

 intervals. Cannon connects it in part with the consistency of the 

 food, but mainly with the effect of the hydrochloric acid in the 



* See Osier, "Journal of the American Medical Association," Nov. 15, 

 1902, for life of Beaumont and account of his work. 



t See Cannon, "American Journal of Physiology," 1, 359, 1898; and Roux 

 and Balthazard, "Archives de Physiologic," 10, 85, 1898. 



J Hofmeister and Schiitz, loc. "cit. 



Moritz, "Zeitschrift f. Biologic," 32, 359, 1895. 



