MOVEMENTS OF THE ALIMENTARY CANAL, ETC. 379 



observations all tend to show that the main movements of the stomach are 

 effected by the musculature of the antrum pylori, whose contraction is not only 

 the chief factor in ejecting the material into the duodenum, but also aids in 

 keeping the contents of the stomach in motion. The extent to which contrac- 

 tions occur in the fundic end of the stomach does not seem to be so clearly de- 

 termined. According to some observers rhythmic movements are absent in the 

 fundus to the left of about the middle of the stomach, this portion simply re- 

 maining in a condition of tone ; according to others the contractions begin near 

 the oesophageal opening and pass thence toward the pylorus. According to 

 Cannon's observations on the cat, the fundic end toward the close of digestion 

 enters into a gradually increasing condition of tone that squeezes its contents 

 forward into the pre-antral region. 



According to Hofmeister and Sehiitz, a normal movement begins near the 

 cardia by a flattening or constriction which is feeble and is apparent only on 

 the side of the great curvature. This constriction is due to a contraction of 

 the circular muscle-fibres, and the wave thus started passes toward the pylorus, 

 increasing in strength as it goes, while the parts behind previously in contrac- 

 tion slowly relax. This peristaltic wave comes to a stop a short distance in 

 front of the antrum pylori by a constriction involving the whole circumference 

 of the stomach, to which these authors gave the name of the "pre-antral" 

 constriction ; it seems to mark the climax of the peristaltic movement. The 

 obvious effect of this movement so far would be to push forward some of the 

 contents of the fundus into the antrum. Immediately upon the formation of 

 this constriction the strong " sphincter antri pyloric! " or transverse band which 

 marks the beginning of the antrum, contracts strongly — so strongly, in fact, in 

 what may be considered normal movements, as to cut off entirely the antrum 

 pylori from the fundus. Following upon this the musculature of the antrum 

 contracts as a whole, squeezing upon its contents and sending them through the 

 narrow opening of the pylorus into the duodenum. If, however, the contents 

 of the antrum are not entirely liquid, but contain some solid particles too huge 

 to escape through the narrow pylorus, their presence seems to stimulate an 

 " antiperistaltic" wave in the musculature of the antrum pylori — that is, a mus- 

 cular wave running in the reverse direction to that of a normal one, from right 

 to left, the effect of which is to throw back these solid particles into the fundus, 

 which is now in communication with the antrum, the sphincter antri pyloric! 

 having relaxed. This reversed wave in the antrum seems to have been observed 

 repeatedly by Beaumont upon the human stomach, as well as by Hofmeister 

 and Sehiitz upon the dog's stomach, and enables us to understand how solid 

 particles thrown against the pylorus arc again forced back into the fundus to 

 undergo further digestive and mechanical action. According to other 

 observers, the contractions of the sphincter antri pyloric) arc not strong 

 enough to cut off completely the antrum, and the antrum does not contract a- 

 a whole. The peristaltic waves simply run over this portion with increasing 

 strength forcing the food against the pylorus. These movements, a- a 

 whole, from fundus to pylorus occur with a certain rapidity which varies 



