THE STOMACH. 1165 



merges with a slight curve into the lesser curvature of the stomach, while ou the 

 left side there is a deep notch, the incisura cardiaca, between the inferior end of 

 jhe oesophagus and the fundus, in which lies a strong projecting ridge of the 

 right crus of the diaphragm. 



This notch on the outer surface produces a fold in the interior of the stomach, 

 vvhich may assist in closing the cesophageal opening, and this, with the decussating 

 fibres of the diaphragm, and the strengthened circular fibres of the inferior end of the 

 oesophagus, forms a kind of sphincter for this orifice which serves to prevent 

 regurgitation from the stomach under ordinary condition. 



The cardia is very deeply placed, and lies about four inches behind the sternal 

 ,3nd of the seventh left costal cartilage, at a point one inch from its junction 

 vvith the sternum. Posteriorly it corresponds to the level of the eleventh thoracic 

 vertebra. 



Owing to the fixation of the oesophagus by its passage through the diaphragm, and the close 

 ;onnexion between the stomach and the diaphragm, near the cardia where the peritoneum is 

 ibsent, this is the most fixed part of the whole organ. The object of this immobility is 

 evidently to maintain a clear passage for the food entering the stomach. 



Pylorus. The pyloric orifice or pylorus is the aperture by which the stomach 

 jommunicates with the duodenum. It is placed at the extremity of the pyloric 

 ind of the stomach, and its position is indicated upon the surface of the stomach 

 jy a slight annular constriction which is most marked at the curvatures. 



Its position is also indicated by an arrangement of blood-vessels at the pyloric ring, which is 

 learly constant. On the peritoneal surface a thick vein passes upwards from the lower side 

 somewhat more than half-way on the anterior surface, and from the upper border a second vein 

 'caches downwards in the same line, nearly, if not quite, meeting the first (W. J. Mayo). 

 . 



The pyloric constriction marks the junction of stomach and duodenum, and 

 jhere the various coats of these portions meet with one another. The peritoneal 

 iovering of the stomach is continued onwards on to the first part of the duodenum. 

 At the pylorus the muscular fibres have a special arrangement, which is due 

 ;0 the presence of a mechanism for arresting the escape of food from the stomach 

 oefore it has undergone digestion. The longitudinal fibres of the stomach (stratum 

 ; .ongitudinale) are in part continued onwards into the longitudinal fibres of the 

 luodenal coat, but many of them bend inwards into the thickened ring around the 

 ' )pening, where they spread out in diverging bundles, which interlace with the most 

 i superficial of the circular fibres, and some of them reach and terminate in the 

 subjacent submucosa. 



The circular muscular fibres of the stomach (stratum circulare) are not 

 : continuous directly with those of the duodenum. On the contrary, at the orifice 

 -hey become very much increased in number, and they form a thick ring, or 

 sphincter, which is separated from the circular muscular coat of the duodenum 

 )y a fibrous septum. 



The length of this sphincteric ring is not easily estimated, for while it is 

 sharply marked off from the duodenum there is no sharp line of demarcation on 

 she gastric side. There the ring gradually merges into the circular muscular coat 

 >)f the cylindrical pyloric canal. 



When the pyloric canal is contracted, its wall is nearly as thick as the sphinc- 

 eric ring. 



The gastric mucous membrane (tunica muscosa) is continued into the mucous 

 neinbra.ne of the duodenum at the distal margin of the sphincter. The junction 

 cannot be recognised by superficial inspection. The gastric mucosa is considerably 

 < -hickened where it covers the sphincter muscle. When examined post-mortem in 

 * ;he ordinary way, the aperture, viewed from the duodenal side, is somewhat oval in 

 brai. When seen from the opposite side, it presents an irregular or stellate 

 Appearance, owing to the fact that the rugse of the gastric mucous membrane are 

 Continued up to the orifice. 



The orifice is directed horizontally backwards, and to the right. When the 

 stomach is full, however, it looks almost directly backwards, or even slightly to the 

 eft side. 



