in DIGESTION IN THE MOUTH AND STOMACH 185 



changes its form and position ; the lower, great curvature moves 

 forward, and the upper, small curvature turns backward. This is 

 effected, when the walls become distended, by a passive rotation of 

 the stomach round its axis, which passes through the fixed points 

 represented by the cardia and the pylorus. 



As the stomach fills with food, a series of active movements are 

 set up which proceed from the cardia along the body of the 

 stomach, and terminate at the pyloric orifice. They are peristaltic 

 in character, the mass of ingesta being churned up, and driven 

 towards the pyloric antrum and back along the lower curvature, 

 so that the upper portion of the gastric contents is continually 

 forced down below. These peristaltic movements are sometimes 

 accompanied by antiperistaltic contractions, which originate in the 

 pylorus, and proceed towards the cardia, but usually stop about 

 half-way down the stomach. The double movement helps to 

 mix up the mass of ingesta, and to saturate it with the gastric 

 juice. At the beginning of digestion the contractions are weak 

 and irregular ; afterwards they become more active, to decrease and 

 die away when the formation of chyme is completed. 



The evacuation of the stomach during digestion is commonly 

 supposed to be effected by a rhythmical closing and opening of the 

 pyloric sphincter. 



These data are mainly due to the observations of Wepfer, 

 Schwartz, Haller, Spallanzani, Magendie, Beaumont. Wepfer 

 (1679) was the first to describe active peristaltic and anti- 

 peristaltic movements of the stomach ; Magendie (1838) first 

 noted a constriction of the stomach due to the muscles of the 

 pyloric antrum ; Beaumont (1834) first observed most of the 

 phenomena enumerated in man. Ponsgen (1882) published a 

 monograph on the motor functions of the stomach, which reviews 

 the entire literature of the subject, and cites over 500 authors. 



Morat (1882) used a gastric sound attached to a large rubber 

 balloon with thin walls, which could be inflated with air, the 

 other end of the sound being connected with a tambour. With 

 this he recorded three kinds of abdominal movements on man and 

 dogs respiratory (predominating), cardiac, and gastric ; but this 

 method obviously tells nothing as to the form and localisation of 

 the peristaltic movements. 



Pfungen (1887), by the manometric method, succeeded in 

 counting on an average three contractions of the antrum per 

 minute, each lasting 6-12 sees. He noted, in confirmation of an 

 observation by Hofmeister and Schiitz, that ?olid bodies introduced 

 into the antrum were driven back towards the fundus of the 

 stomach by an antiperistaltic movement. 



Moritz (1895), with an elastic balloon of medium size attached 

 to the end of a flexible sound passed through the oesophagus, 

 registered the variations of gastric pressure, and recorded the 



