CH. xxxv.] VOMITING. 5 2 5 



coeliac ganglion, and ultimately pass to the stomach by the 

 splanchnic nerves. 



It seems probable that automatic peristaltic contraction is 

 inherent in the muscular coat of the stomach, and that the 

 central nervous system is only employed to regulate it by impulses 

 passing down by the vagi or splanchnic nerves. 



The secretory nerves of the gastric glands are treated on p. 482. 



VOMITING. 



The expulsion of the contents of the stomach in vomiting, like 

 that of mucus or other matter from the lungs in coughing, is 

 preceded by an inspiration ; the glottis is then closed, and 

 immediately afterwards the abdominal muscles strongly act ; but 

 here occurs the difference in the two actions. Instead of the vocal 

 cords yielding to the action of the abdominal muscles, they 

 remain tightly closed. Thus the diaphragm being unable to go 

 up, forms an unyielding surface against which the stomach can 

 be pressed. At the same time the cardiac sphincter-muscle being 

 relaxed, and the orifice which it naturally guards being dilated, 

 while the pylorus is closed, and the stomach itself also con- 

 tracting, the action of the abdominal muscles expels the contents 

 of the organ through the oesophagus, pharynx, and mouth. The 

 reversed peristaltic action of the oesophagus possibly increases 

 the effect. 



It has been frequently stated that the stomach itself is quite 

 passive during vomiting, and that the expulsion of its contents is 

 effected solely by the pressure exerted upon it when the capacity 

 of the abdomen is diminished by the contraction of the diaphragm, 

 and subsequently of the abdominal muscles. The experiments 

 and observations, however, which are supposed to confirm this 

 statement, only show that the contraction of the abdominal 

 muscles alone is sufficient to expel matters from an unresisting 

 bag through the oesophagus ; and that, under very abnormal 

 circumstances, the stomach, by itself, cannot expel its contents. 

 They by no means show that in ordinary vomiting the stomach is 

 passive, for there are good reasons for believing the contrary. In 

 some cases of violent vomiting the contents of the duodenum are 

 passed by anti-peristalsis into the stomach, and are then vomited. 

 \\ he-re there is obstruction to the intestine, as in strangulated 

 hernia, the contents of all the small intestine may be vomited. 



Nervous mechanism. Some few persons possess the power 

 of vomiting at will, or the power may be acquired by effort and 

 practice. But normally the action is a reflex one. 



Thea/erent nerves are principally the fifth, and glossopharyngeal 



