730 PHYSIOLOGY OF DIGESTION AND SECRETION. 



Goltz* has shown that in dogs in which the spinal cord had 

 been severed in the lower thoracic region defecation was per- 

 formed normally. In later experiments, in which the entire spinal 

 cord was removed except in the cervical and upper part of the 

 thoracic region, it was found that the animal, after it had re- 

 covered from the operation, had normal movement once or twice 

 a day, indicating that the rectum and lower bowels acted by virtue 

 of their intrinsic mechanism. An interesting result of these ex- 

 periments was the fact that the external sphincter suffered no 

 atrophy, although its motor nerve was destroyed, and that it 

 eventually regained its tonic activit^^ 



Vomiting.^The act of vomiting causes an ejection of the con- 

 tents of the stomach through the esophagus and mouth to the 

 exterior. It was long debated whether the force producing this 

 ejection comes from a strong contraction of the walls of the stom- 

 ach itseK 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, f 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 



* "Archiv f. die gesammte Physiologie," S, 160, 1874; 63, 362, 1896. 

 t Openchowski, "Archiv f. Physiologie," 1899, p. 552. 



