MOVEMENTS OF THE STOMACH. 201 



toward the pylorus, but it is also thoroughly mixed with the 

 gastric juice, and thus the action of the latter is more compltee 

 and efficient than it otherwise would be. 



Experiments of Cannon. We deem a somewhat detailed account 

 of these experiments warranted, for the reason that, although 

 they were made upon the cat, the evidence is conclusive that the 

 character of the movements of the human stomach during diges- 

 tion differs in no essential particular from that of the movements 

 of the stomach of the animal which was the subject of experi- 

 mentation. 



Cannon and Day state that " observations with the x-rays have 

 proved that the stomach of the cat is like that of the dog, rat, rab- 

 bit, guinea-pig, and man, in being separable into two parts : the 

 quiet cardiac end and the active pyloric end. Moreover, the mucosa 

 of the cat's stomach resembles that of the dog and of man, not 

 only in structure but also in pouring out an active secretion from 

 almost every part of its surface." 



Movements of the Pyloric Part. Within five minutes after a 

 cat has finished a meal of bread mixed with subnitrate of bismuth 

 there is visible near the duodenal end of the antrum a slight 

 annular contraction which moves peristaltically to the pylorus ; 

 this is followed by several waves recurring at regular intervals. 

 Two or three minutes after the first movement is seen, very 

 slight constrictions appear near the middle of the stomach, and, 

 pressing more deeply into the greater curvature, course slowly 

 toward the pyloric end. As new regions enter into constriction 

 the fibers just previously contracted become relaxed, so that 

 there is a true moving wave, with a trough between two crests. 

 When a wave swings round the bend in the pyloric part the 

 indentation made by it deepens, and as digestion goes on the 

 antrum elongates and the constrictions running over it grow 

 stronger, but, until the stomach is nearly empty, do not divide the 

 cavity. After the antrum has lengthened, a wave takes about 

 thirty-six seconds to move from the middle of the stomach to the 

 pylorus. At all periods of digestion the waves recur at intervals 

 of almost exactly ten seconds. It results from this rhythm that 

 when one wave is just beginning several others are already run- 

 ning in order before it. Between the rings of constriction the 

 stomach is bulged out (Figs. 109-111). In one experiment the 

 cat was fed 15 grams of bread at 10.25 A.M. The waves were 

 running regularly at 11 o'clock. The stomach was not free 

 from food until 6.12 P.M. At the rate of 360 waves per hour, 

 approximately 2600 waves passed over the antrum during the 

 single digestive period. 



Movements of the Pyloric Sphincter. Ten or fifteen minutes 

 elapse after the first constriction of the antrum before food appears 



