CHAPTER LII 

 THE MECHANISMS OF DIGESTION (Cont'd) 



THE MOVEMENTS OF THE STOMACH 



The Character of the Movements 



Even from the earliest days it has been recognized that the stomach 

 performs two important functions: (1) receiving the swallowed food 

 and then discharging it slowly into the intestine, and (2) initiating the 

 chemical processes of digestion. In order to understand the mechanism 

 by which the stomach collects and then discharges the food, it is neces- 

 sary first of all to recall certain anatomic facts concerning the organ, 

 and for this purpose it is most convenient to accept the description 

 given by Cannon, which is illustrated in the accompanying figure. The 

 organ is divided into a cardiac and a pyloric portion by a deep notch in 

 the lesser curvature, called the incisura angularis. The cardiac portion 

 is further subdivided into two by the cardiac orifice. The part which 

 lies, in man, above a line drawn horizontally through the cardia is the 

 fundus. The part lying between the fundus and the incisura angularis 

 is known as the body of the stomach, which, when full, has a tapering 

 shape. The pyloric portion lying on the right of the incisura angularis 

 is further divided into two parts: the pyloric vestibule and the pyloric 

 canal, the latter of which lies next the pyloric sphincter and in man 

 measures about 3 cm. in length (see Fig. 154). 



The filled stomach of a person standing erect is so disposed that the 

 greatest curvature forms its lowest point, which may be considerably 

 below the umbilicus. As digestion proceeds and the stomach empties, 

 the greater curvature becomes gradually raised, so that ultimately the 

 pylorus comes to be the most dependent part of the stomach. From 

 these and many other observations it is certain that the emptying of the 

 stomach does not at all depend on the operation of the force of gravity. 

 Indeed, that this can not be the case is perfectly clear, when we con- 

 sider the disposition of the stomach in quadrupeds. 



Exact observation on the movements which the stomach performs from 

 the time it is filled with food till it empties, have been made by the 

 x-ray method, first introduced by Cannon. 12 The method consists in feed- 



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