406 OF FOOD, AND THE DIGESTIVE PROCESS. 



compel them, at the same time, to revolve about the interior from point to 

 point, and from one extremity to the other." In addition to these movements, 

 there is a constant agitation of the stomach, produced by the respiratory muscles. 



Fie. 120. 



A Tiew of the interior of the Stomach and Duodenum in situ, the inferior portion of each having been re- 

 moved : 1, 1, the under side of the liver ; 2, the gall-bladder ; 3, 3, the lesser curvature and anterior faces, as 

 seen from below ; 4, the rugae, about the cardiac orifice ; 5, the pyloric orifice ; 6, the rugae, and thickness of 

 this orifice; 7, 7, the duodenum; 8, lower end of the right kidney. 



The motions of the stomach itself are not performed on any very exact plan, and 

 are much influenced by the character of the ingesta, the state of the general system, 

 and by other circumstances. The following is the ordinary course, however, of 

 the revolutions of the food. " After passing the oesophageal ring, it moves from 

 right to left, along the small arch ; thence through the large curvature, from left 

 to right. The bolus, as it enters the cardia, turns to the left, passes the aperture, 

 descends into the splenic extremity, and follows the great curvature towards the 

 pyloric end. It then returns, in the course of the smaller curvature, makes its 

 appearance again at the aperture in its descent into the great curvature, to 

 perform similar revolutions. These revolutions are completed in from one to 

 three minutes. They are probably induced, in a great measure, by the circular 

 or transverse muscles of the stomach. They are slower at first, than after chy- 

 myfication has considerably advanced ;" at which time also there is an increased 

 impulse towards the pylorus. It is probable that, from the very commencement 

 of chymification until the organ becomes empty, portions of chyme are continu- 

 ally passing into the duodenum ; for the bulk of the alimentary mass progressively 

 diminishes, and this the more rapidly as the process is nearer its completion. 

 The accelerated expulsion appears to be effected, by a peculiar action of the trans- 

 verse muscles; and especially of that portion of them which surrounds the 

 stomach at about four inches from its pyloric extremity. This band is so forcibly 

 contracted in the latter part of the digestive process, that it almost separates the 

 two portions of the stomach into a sort of hour-glass form; and Dr. B. states 

 that, when he attempted to introduce a long thermometer-tube into the pyloric 

 portion of the stomach, the bulb was at first gently resisted, then allowed to pass, 

 and then grasped by the muscular parietes beyond, so as to be drawn in; whence 

 it is evident that the contraction has for its object, to resist the passage of solid 

 bodies into the pyloric extremity of the stomach, at this stage of digestion, whilst 

 the matter which has been reduced to the fluid form is pumped away (as it were) 

 by the action of that portion of the viscus. These peculiar motions continue 

 until the stomach is perfectly empty, and not a particle of food or chyme remains ; 

 and when they are nearly brought to a close, the contraction of the pyloric orifice 

 also gives way to an extent sufficient to allow not only the undigested residue 

 of the food, but also large solid bodies that may have been swallowed (such as 

 coins and the like), to pass into the intestinal canal. 



