MOVEMENTS OF THE ALIMENTARY CANAL. 673 



itself or whether it is due mainly to the action of the walls of the 

 abdomen. A forcible spasmodic contraction of the abdominal 

 muscles takes place, as may easily be observed by any one upon 

 himself, and it is now believed that the contraction of these muscles 

 is the principal factor in vomiting. Magendie found that if the 

 stomach was extirpated and a bladder containing water was sub- 

 stituted in its place and connected with the esophagus, injection 

 of an emetic caused a typical vomiting movement with ejection of 

 the contents of the bladder. Gianuzzi showed, on the other hand, 

 that upon a curarized animal vomiting could not be produced by an 

 emetic because, apparently, the muscles of the abdomen were 

 paralyzed by the curare. There are on record a number of ob- 

 servations which tend to show that the stomach is not passive 

 during the act. On the contrary, it may exhibit contractions, more 

 or less violent in character. According to Openchowski,* the 

 pylorus is closed and the pyloric end of the stomach firmly con- 

 tracted so as to drive the contents toward the dilated cardiac por- 

 tion. Cannon states that in cats the normal peristaltic waves pass 

 over the pyloric portion in the period preceding the vomiting and 

 that finally a strong contraction at the "transverse band" com- 

 pletely shuts off the pyloric portion from the body of the stomach, 

 which at this time is quite relaxed. The act of vomiting is, in fact, 

 a complex reflex movement into which many muscles enter. The 

 following events are described : The vomiting is usually preceded by 

 a sensation of nausea and a reflex flow of saliva into the mouth. 

 These phenomena are succeeded or accompanied by retching move^ 

 ments, which consist essentially in deep, spasmodic inspirations with 

 a closed glottis. The effect of these movements is to compress the 

 stomach by the descent of the diaphragm, and at the same time to 

 increase decidedly the negative pressure in the thorax, and therefore 

 in the thoracic portion of the esophagus. During one of these 

 retching movements the act of vomiting is effected by a convulsive 

 contraction of the abdominal wall that exerts a sudden additional 

 strong pressure upon the stomach. At the same time the cardiac 

 orifice of the stomach is dilated, possibly by an inhibition of the 

 sphincter, and according to the above description the fundic end 

 of the stomach is also dilated, while the pyloric end is in strong 

 contraction. The stomach contents are therefore forced violently 

 out of the stomach through the esophagus, the negative pressure in 

 the latter probably assisting in the act. The passage through the 

 esophagus is effected mainly by the force of the contraction of the 

 abdominal muscles; there is no evidence of antiperistaltic move- 

 ments on the part of the esophagus itself. During the ejection of 

 the contents of the stomach the glottis is kept closed by the adductor 



* " Archiv f . Physiologie, " 1889, p. 552. 

 43 



