THE MECHANICS OF DIGESTION 1011 



remember that unless the fistulous communication is yery large, the 

 food will nevertheless pass through the pylorus. Consequently, the 

 pyloric obstruction must be rather complete before the fistula can 

 serve its purpose. Secondly, it has been observed in animals that 

 some of the material which has left the stomach by way of the pylorus 

 again enters this organ through the fistulous communication. Thirdly, 

 the outpouring of the acid gastric juice into intestinal segments which 

 are normally not directly exposed to it, may lead to erosions and ulcera- 

 tions of the mucosa, and especially if the blood- or nerve-supply have 

 in any way been interfered with during the operation. Consequently, 

 such a communication should not be established in the absence of 

 organic disease of the pylorus. 



Vomiting. — The act of vomiting is a complex reflex in which 

 different muscles take part and which is usually preceded by a sensa- 

 tion of nausea, a reflex secretion of saliva, and other symptoms of a 

 more general character. In the suckling it consists essentially of a 

 contraction of the musculature of the stomach and a relaxation of the 

 esophagus and presents, therefore, the simplest possible details. In 

 the adult, on the other hand, other factors are brought into play, 

 chief among which is the abdominal press. The latter consists in a 

 spasmodic contraction of the abdominal muscles, inclusive of the 

 diaphragm, following a short inspiration and closure of the glottis. 

 It is apparent, however, that in the adult the stomach plays a rather 

 subordinate part, as is evinced by the fact that the retching movements 

 occurring at the beginning of the act of vomiting, which are wholly 

 of gastric origin, are altogether too weak to eject the gastric contents. 

 Moreover, it has been shown by Gianuzzi that this act cannot be 

 evoked in curarized animals, because this agent paralyzes the muscles 

 of the abdomen. In addition, it has been proved by Magendie that 

 vomiting also results in animals whose stomach has been replaced 

 by a bladder filled with water. 



During the act of vomiting the peristalsis is abolished, although 

 intense movements of this kind may take place shortly beforehand. 

 Irregular retching motions then result which, however, do not seem to 

 be antiperistaltic in their character. The essential factor concerned 

 in vomiting, is the production of a high intragastric pressure, which, 

 as we have just seen, is the direct result of the contraction of the 

 abdominal muscles and smooth musculature of the stomach. The 

 pylorus is tightly closed at this time, while the cardiac sphincter and 

 esophagus are relaxed.^ An eructation of gas frequently precedes 

 this act, in fact, many animals such as the dog hasten its occurrence by 

 distending the stomach with freshly swallowed air. Vomiting also 

 necessitates a forward movement of the hyoid bone and larynx, 

 as well as a projection of the mandible. Both measures serve to 

 straighten the channel of ejection. Although the nasal cavity is 

 partly protected against the ingress of vomited material by the con- 

 1 Openchowski, Archiv fur Physiol., 1889, 552. 



