380 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



with the nature and amount of the contents of the stomach and the period of 

 digestion. In Beaumont's observations the movements of the pylorus are 

 recorded as following each other at intervals of two to three minutes, while 

 upon cats, according to Cannon's observations, the peristaltic waves in the 

 pyloric part follow at regular intervals of about ten seconds. 



It will he seen that according to this description the movements occur in 

 two phases: first, the feeble peristaltic movement running over the fundus 

 chiefly .m the side of the great curvat ure and resulting in pushing some of 

 the fundic contents into the antrum ; second, the stronger contractions of the 

 antrum, the effect of which is to squeeze some of the contents into the duo- 

 denum. Whether or not the musculature of the antrum shows only stronger 

 peristaltic waves, or contracts as a whole, with some suddenness after the 

 manner of a systole, as described by Hofmeister and Schiitz, cannot be 

 definitely stated. The force with which the contents of the antrum are 

 ejected through the pylorus into the duodenum, as shown by observations 

 made upon animals with a duodenal fistula, speaks in favor of the latter 

 view. It is possible that either of these phases, but especially the tirst, 

 might occur at times without the other, and in the first phase it is probable 

 that the longitudinal fibres of the stomach also contract, shortening the 

 organ in its long diameter and aiding in the propulsive movement, but 

 actual observation of this factor has not been successfully made. It can 

 well be understood that a series of these movements occurring at short inter- 

 vals would result in putting the entire semi-liquid contents of the stomach 

 into constant circulation. The precise direction of the current set up is not 

 agreed upon, but it is probable that the graphic description given by Beaumont 

 is substantially accurate. A portion of this description may be quoted, as fol- 

 lows : "The ordinary course and direction of the revolutions of the food are, 

 first, after passing the oesophageal ring, from right to left, along the small 

 arch; thence, through the large curvature, from left to right. The bolus, as it 

 eniers the cardia, turns to the left ; passes the aperture ; descends into the splenic 

 extremity, and follows the great curvature toward the pyloric end. It then 

 returns in the course of the small curvature." The average time taken for one 

 of these complete revolutions, according to observations made by Beaumont, 

 seems to vary from one to three minutes. 



It is possible, of course, thai this typical circuit taken by the food may often 

 be varied more or less by different conditions, but the muscular movements 

 observed from the outside would seem to be adapted to keeping up a general 

 revolution of the kind described. The general result upon the food may easily 

 be imagined. It becomes thoroughly mixed with the gastric juice and any liquid 

 which may have been swallowed, and is gradually disintegrated, dissolved, and 

 more or less completely digested so far as the proteid and albuminoid constitu- 

 ent- are concerned. The mixing action is aided, moreover, by the movements 

 of the diaphragm in respiration, since at each de-cent it presses upon the stomach. 

 The powerful muscular contractions of the antrum serve also to triturate the 

 softened solid particle-, and finally the whole mass is reduced to a liquid or 



