236 DIGESTIVE SYSTEM. 



be instantly followed by liquid stools, the water which enters 

 the great intestine directly after being swallowed producing 

 the effect of an injection. 



Vomiting. Apart from this peculiar function of the mus- 

 cular necklace or band placed along the smaller curvature, 

 the mechanical role of the muscular coats is, as we have said, 

 of little importance. Thus, the stomach takes scarcely any 

 part in the movements of regurgitation made in vomiting : 

 it rejects its contents under the influence of the pressure ex- 

 ercised by the diaphragm and the muscles of the abdominal 

 coats. Recent investigations by SchilF, however, show that 

 if the muscular coat or tunic of the stomach does not pro- 

 duce the effort of vomiting, in order to throw off the con- 

 tents of the viscera, it at least serves to aid in this rejection. 

 To this end the longitudinal fibres of the cardiac region con- 

 tract, and then, straightening their curve, distend the corre- 

 sponding orifice. The attempt to vomit succeeds only when 

 the abdominal pressure takes place simultaneously with this 

 dilatation of the cardia. The pneumo-gastric nerve regulates 

 the association of these movements. 1 



Vomiting is a reflex action resembling that of sneezing. 

 (See p. 47.) The agents by which it is excited act upon the 

 nerve centres either directly, or by the intervention of various 

 sensory nerves, as the pneumo-gastric and the gloss o-pharyn- 

 geal nerves. Those which act by means of this latter nerve, 

 are called nauseous (see sense of taste; the glosso-pharyngeal 

 a nauseous nerve) the rest are simply vomitive. 



II. The columnar epithelium of the stomach exerts a pro- 

 tecting influence over this viscus : and prevents it from 

 digesting itself; but, if the epithelium be injured in any part, 

 the gastric juice acts upon the subjacent parts of the coats 

 of the stomach, producing an erosion known in pathology 

 under the name of round ulcer. The epithelium is here, as 



fluids, however, could pass with the greatest ease from the pylorus to 

 the cardia, or inversely, without mingling with the aliments contained 

 in the cardiac portion, the latter being strongly pressed against its 

 contents, which it thus prevented from passing out, or from being 

 penetrated by the fluids. 



** This fact justifies the hypothesis set forth by Luschka, and by 

 Professor Kiiss in his lectures, which attributes to the oblique fibres, 

 in certain cases, the power of establishing a direct communication 

 between the orifices of the cardia and the pylorus." 



1 M. Schiff, " Lemons sur la Physiologic de la Digestion.' 7 

 1867, Vol. II., 37th lecon. 



