MOVEMENTS OF THE ALIMENTARY CANAL. 717 



special development of this layer functions as a sphincter pylori, 

 which with the aid of a circular fold of the mucous membrane 

 makes it possible to shut off the duodenum completely from the 

 cavity of the stomach. The hne of separation between the antrum, 

 pylori and the body of the stomach is made by a special thicken- 

 ing of the circular fibers which forms a structure known as the 

 "transverse band" by the older writers.* Under certain condi- 

 tions, such as vomiting, stimulation of the vagus, etc., this band 

 may be contracted with such force as to separate the antrum 

 entirely from the fundic end of the stomach. 



The Movements of the Stomach. — The solid food remains in 

 the stomach for several hours, and during this time the musculature 

 contracts in such a way that the thinner portions as they are formed 

 by digestion are ejected from time to time through the pylorus into 

 the intestine. Except at the definite intervals when the pyloric 

 sphincter relaxes the food is entirely shut off from the rest of the 

 alimentary canal by the tonic closure of the sphincters at the cardia 

 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, wliich 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. t In recent years the subject has been studied with great 

 success by means of the a:-rays, t on the excised stomach, § and by 

 means of tambours or sounds introduced into the stomach to 

 measure the pressure changes. 1 1 These researches all unite in em- 

 phasizing one fundamental point — namely, that the fundic end 

 of the stomach is less 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 mainly trit- 

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

 duodenum. According to the observations made with the x-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 



* See Beaumont, "Physiology of Digestion," second edition, 1847, p. 104. 



t 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 Physiologie," 10, 85, 1898. 



§ Hofmeister and Schiitz, loc. cit. 



II Moritz, "Zeitschrift f. Biologie," 32, 359, 1895. 



