111 DIGESTION IN THE MOUTH AND STOMACH 195 



some hard boluses of bismuth subnitrnte with the soft foods, the 

 pyloric sphincter is seen, radioscopically, to close sharply on the 

 arrival of the bolus. 



These results are particularly important because they confirm 

 to a great extent for uninjured man or animals, the observations 

 made by means of fistulae, or other methods, in which the normal 

 conditions of gastric digestion have been more or less modified. 



X. Since it is one of the most important modifications of the 

 ordinary motor processes in the 'stomach, special attention must be 

 given to vomiting. In the majority of cases it is a pathological 

 phenomenon, but is under certain conditions a true physiological 

 act, by which the body relieves the stomach of excessive work, and 

 eliminates noxious substances ingested or developed in situ by 

 abnormal processes of fermentation. Vomiting is excited either 

 by excessive distension of the stomach, or by the acrid substances 

 developed in abnormal digestive processes, or by the action of the 

 so-called emetics which are particularly adapted to excite the 

 nervous mechanisms that give rise to vomiting. 



The fundamental question in regard to the mechanism of 

 vomiting is to decide what part the stomach plays by its con- 

 tractions, and what is due to abdominal compression, which 

 consists in the synchronous contraction of the abdominal and 

 diaphragmatic muscles. 



The older physicians held vomiting to be purely an effect of 

 the antiperistaltic movements of the stomach, with simultaneous 

 closure of the pylorus and dilatation of the cardia. Bayle and 

 Chirac, and after them Magendie, sustained the opposite opinion, 

 viz. that the stomach was passive in vomiting, and that the 

 process rests upon the violent impulse of abdominal com- 

 pression. 



Schwartz demonstrated that the stomach, when exposed and 

 freed from the pressure of the abdominal muscles and diaphragm, 

 was no longer capable of emptying itself by vomiting on injection 

 of tartar emetic. He did not, however, deny the active participa- 

 tion of the stomach. Mageudie (1813), went farther. He was 

 unable to convince himself of such participation, either by 

 palpation or by inspection. It appeared to him to be an 

 experimentum crucis that vomiting was accomplished perfectly 

 when the stomach was replaced by a pig's bladder filled with 

 water. Giannuzzi (1866) supported this theory by his observation 

 that curarised dogs could not vomit when tartar emetic was 

 injected. 



But this fact does not prove that the stomach is passive, only 

 that vomiting requires the aid of abdominal compression. Tantini 

 (1825) was the first to prove this by a modification of Magendie's 

 experiment in which he substituted a bladder for the stomach, 

 but without interfering with the cardiac orifice. Under these 



