THE MECHANISMS OF DIGESTION 491 



THE EMPTYING OF THE STOMACH 



The Control of the Pyloric Sphincter 



Recent experimental work demands that the view originally advanced 

 by Pavlov and elaborated by Cannon, namely that the acidity of the 

 chyme constitutes the chief factor in the control of the pyloric sphincter, 

 be abandoned. This conception of the pyloric mechanism fails to account 

 for the rapid passage of w^ater and egg white into the duodenum, and 

 leaves unexplained the normal emptying time of the stomach in certain 

 pathological states in which the secretion of acid is suppressed or greatly 

 reduced. 



From the study of serial radiographs Cole 30 showed that in man a def- 

 inite relationship existed between the movements of the antrum and those 

 of the pyloric sphincter. The activities of the sphincter were found to 

 be directly proportional to the magnitude of the antral contractions; 

 Avhen the motility of the antrum was low the sphincter contractions were 

 feeble, powerful antral waves on the other hand were associated with 

 vigorous sphincter movements. Chyme passed into the duodenum during 

 gastric systole but not during diastole. Luckhardt, Phillips and Carl- 

 son 31 combining fluoroscopic observations with graphic records, obtained 

 by means of a balloon inserted into the stomach, have shown that the 

 passage of chyme into the duodenum coincides with peristaltic waves 

 travelling over the stomach. The gastric contents collected from a duode- 

 uostomy made immediately below the pyloric sphincter rarely showed the 

 presence of free acidity as tested by congo-red. It has been noted that water 

 placed in the stomach passed through the sphincter in gushes of varying 

 intervals apart, but the emissions on the whole showed evidence of 

 rhythm and it was assumed on this account that they were dependent 

 upon peristaltic waves (Ivy). The water as it left the stomach was 

 neutral in reaction. 



These observations in the main have been confirmed and extended 

 by other investigators. The more precise study of the interdependence 

 of the antral and sphincter movements has been made by Wheelon and 

 Thomas 32 who combined the study of radiographs with graphic records 

 obtained by balloons placed respectively in the antrum and pyloric 

 canal. In this manner tracings could be taken of movements occurring 

 simultaneously in the two regions. These observers find that when 

 the peristaltic wave commencing in the body of the stomach and trav- 

 elling over the vestibule reaches the antrum the sphincter becomes 

 relaxed so that any material swept forward by the constricting wave is 

 free to pass through the pyloric opening. The wave is sufficiently 

 broad to involve the whole antrum at one time and indeed it involves 



