MOVEMEOTS OF THE STOMACH. 291 



ach are animated by the pneumogastric nerves and become 

 arrested when both these nerves are divided. 1 



As the result chiefly of the observations of Beaumont, the 

 following may be taken as a summary of the physiological 

 movements of the stomach in digestion : 



The stomach normally undergoes no movements until 

 food is passed into its cavity. When food is received, at the 

 same time that the mucous membrane becomes congested and 

 the secretion of gastric juice commences, contractions of the 

 muscular coat begin, which are slow and irregular during 

 the commencement of stomach-digestion, but become more 

 vigorous and regular as the process advances. After diges- 

 tion has become fully established, the stomach is generally 

 divided by the firm and almost constant contraction of a 

 transverse band of fibres into a cardiac and a pyloric portion ; 

 the former occupying about two-thirds, and the latter one- 

 third of the length of the organ. The contractions of the 

 cardiac division of the stomach are uniform and rather gen- 

 tle ; while in the pyloric division they are intermittent and 

 more expulsive. The effect of the contractions of the stom- 

 ach upon the food contained in its cavity is to subject it to 

 a tolerably uniform pressure, with a certain amount of 

 trituration and agitation, in the cardiac portion, the gen- 

 eral tendency of the movement being toward the pylorus 

 along the greater curvature, and back from the pylorus 

 toward the great pouch along the lesser curvature. At 

 the constricted part, which separates the cardiac from the 

 pyloric portion, there is an obstruction to the passage of the 

 food until it has been sufficiently acted upon by the secre- 

 tions in the cardiac division to have been reduced to a pul- 

 taceous consistence. The alimentary mass then passes into 

 the pyloric division, and by a more powerful contraction 

 than occurs in other parts of the stomach, it is passed into 



1 The question as to how far the sympathetic system of nerves is ever con- 

 cerned in the movements of the stomach will be considered in treating specially 

 of the nervous system. 



