MOVEMENTS OF THE STOMACH 205 



place slowly, by gentle and persistent contractions of the muscular coat ; 

 the food occupying two or three minutes in its passage entirely around 

 the stomach. Every time that a revolution is accomplished, the contents 

 of the stomach are somewhat diminished in quantity ; probably, in a 

 slight degree, from absorption of digested matter by the stomach itself, 

 but chiefly by the gradual passage of the softened and disintegrated 

 mass into the small intestine. This process continues until the stomach 

 is emptied, lasting between two and four hours ; after which, the move- 

 ments of the stomach cease until food is again introduced. 



Regurgitation of food by contractions of the muscular coats of the 

 stomach, eructation, or the expulsion of gas, and vomiting are not 

 physiological acts. It has been shown that vomiting is produced by 

 contractions of the abdominal muscles and the diaphragm, compressing 

 the stomach, which is passive, except that the pyloric opening is firmly 

 closed, the cardiac opening being relaxed. Eructation, although usually 

 involuntary, is sometimes 1 under the control of the will. When it 

 occurs, while it is difficult or impossible to prevent the discharge of the 

 gas, the accompanying sound may easily be suppressed. Eructation 

 frequently becomes a habit, which in many persons is so developed by 

 practice that the act may be performed voluntarily at any time. The 

 gaseous contents of the stomach during digestion consist of oxygen, 

 carbon dioxide, hydrogen and nitrogen, in variable proportions. 



