VOMITING. 297 



portion of its contents suddenly finds its way to the mouth with- 

 out even the consciousness of the individual. The muscular 

 contraction which produces this slight regurgitation is so insig- 

 nificant that there must necessarily have been some relaxation 

 at the cardiac opening of the stomach, which under ordinary 

 conditions is, as we know, firmly closed. The act is then pro- 

 duced, in part by a slight contraction of the abdominal muscles 

 and diaphragm, and in part by contractions of the stomach 

 itself and anti-peristaltic movements of the oesophagus. It 

 has nothing of the violent expulsive character of true vomiting. 



Vomiting.'' The mechanism of vomiting was the subject 

 of much discussion among physiologists in the early part of 

 the present century, when the celebrated experiments of 

 Magendie on this subject were first made. Though Magen- 

 die was by no means the first to demonstrate the view which 

 now generally obtains regarding the muscular actions con- 

 cerned in vomiting, his experiments were of such a striking 

 character, and so demonstratively conclusive, as to attract the 

 attention of all physiologists, and to settle, almost beyond 

 doubt, a question which had before been very uncertain. The 

 experiments of Bayle, Chirac, Schwartz, and others, which 

 tended to prove that vomiting is due to contractions of the 

 abdominal muscles and diaphragm, compressing the stomach, 

 and not to contractions of the muscular tissue of the stomach 

 itself, had been recognized and the conclusions adopted by 

 some physiologists, long before the publication of Magendie's 

 experiments, in 1813. For example, John Hunter, in the 

 second edition of his Animal (Economy, published in 

 1792, says : u We know that the action of vomiting is per- 

 formed entirely by the diaphragm and abdominal muscles. 



5? 2 



1 A sufficient apology for considering the act of vomiting (which is undoubt- 

 edly pathological), so fully as is done in the succeeding pages, is in the fact that 

 its mechanism is usually treated of in works upon physiology, and is not consid- 

 ered in treatises upon practical medicine. 



2 HUNTER, Observations on Certain Paris of the Animal (Economy, London, 

 1792, p. 199. 



