MOVEMENTS OF THE ALIMENTARY CANAL, ETC. 317 



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. The very careful 

 experiments of Hofmeister and Schutz upon the isolated stomach of the dog, 

 together with the reliable observations made by Beaumont under such favora- 

 ble conditions on the human stomach, give us a basis for a description of the 

 sequence and extent of the movements during digestion, which is probably cor- 

 rect in its main features at least, although some of the details still -need investi- 

 gation. 



According to these observers 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 contraction 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 Hofmeister and Schutz 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 pylorici " 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 large 

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

 " antiperistaltic " wave in the musculature of the autrum 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 pylorici 

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

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

 undergo further digestive and mechanical action. These movements, as a 

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

 the nature and amount of the contents of the stomach and the period of diges- 



