206 STOMACH DIGESTION. 



arytenoid muscles ; and the posterior nares are closed by the con- 

 traction of the palatopharyngei muscles or the posterior pillars of 

 the fauces. The cardiac sphincter becoming relaxed, the cardia 

 opens ; while the pyloric sphincter being contracted, the pyloric 

 orifice is closed. The abdominal muscles now contract, and the 

 diaphragm forming a non-yielding wall above the stomach, this 

 organ is so compressed that its contents are forced into the esoph- 

 agus with sufficient power to carry them through the mouth to 

 the exterior. Under some circumstances this force is sufficient to 

 eject them into the posterior nares and out through the nose. 



Although the abdominal muscles are the principal factors in 

 producing the expulsive movements, and indeed are in themselves 

 sufficient, as was demonstrated by Magendie when he removed the 

 stomach and substituted for it a bladder containing water, still 

 there is also a contributing factor in the antiperistaltic contraction 

 of the muscular coat of the stomach. Under some circumstances 

 there is also an antiperistaltic wave in the muscular coat of the 

 small intestine, by which its contents are forced into the stomach 

 and then vomited. Whether this antiperistaltic action occurs or 

 not in the muscular coat of the esophagus is a matter which is 

 still unsettled. 



The above description, which fairly represents the modern views 

 as to the act of vomiting, is modified by the investigations of Open- 

 chonski on dogs and rabbits, and still more recently by Cannon on 

 cats. The former's description is as follows : " As the result of 

 an emetic there occurs a quickening of the walls of the stomach 

 near the pylorus, which appears later in the antral and middle 

 regions of the stomach. This becomes a contraction most marked 

 in the antrum. The fundus enlarges in a spherical form, and into 

 it the contents of the stomach are forced by these contractions of 

 the antrum ; then follow the contractions of the abdominal muscles 

 which force the contents into the esophagus." 



Cannon made his observations upon a cat, to which he gave 

 apomorphin as an emetic. The upper circular muscles relax and 

 become so flaccid that the slightest movement of the abdomen 

 changes the form of the fundus. Then there are apparently 

 irregular twitchings of the fundus wall. Soon a deep constriction 

 starts about three centimeters below the cardia, and, growing in 

 strength, moves toward the pylorus. When it reaches the trans- 

 verse band the constriction tightens and holds fast, while a wave 

 of contraction sweeps over the antrum. Another similar constric- 

 tion follows. In the interval the transverse band relaxes slightly, 

 but tightens again when the second wave reaches it. Perhaps a 

 dozen such waves pass ; then a firm contraction at the beginning 

 of the antrum completely divides the gastric cavity into two parts. 

 This same division of the stomach into two parts at the transverse 

 band is to be seen when mustard is given. Now, although the 

 waves are still running over the antrum, the whole pre-antral 



