STRUCTURE OF STOMACH. 453 



ately, and the surface cleaned ; but, previously, let the student detach the 

 spleen, and cut through the duodenum close to the pylorus. 



Forms and Divisions. The stomach is somewhat conical in form (fig. 

 147). Its size varies much in different bodies, and is sometimes much 

 diminished by a constriction in the centre; when it is moderately dis- 

 tended, it is about twelve inches long and four wide. There are two ends, 

 two orifices, two surfaces, and two borders or curves to be examined. 



Extremities. The left end or tuberosity (fundus ventriculi) is the 

 largest part of the stomach, and projects about three inches to the left of 

 the opening of the oesophagus. The right or pylori c end, much smaller 

 than the other, is cylindrical, and forms the apex of the cone to which the 

 stomach is likened. 



Openings. The left opening (cardiac), which communicates with the 

 oesophagus, is at the highest part of the stomach, and is funnel-shaped 

 towards the cavity of the organ. The right or pyloric orifice opens into 

 the duodenum, and is guarded internally by a muscular band (pylorus) : 

 at the same spot the stomach is slightly constricted externally, where a 

 firm circular ring may be felt. 



Surfaces. The surfaces (anterior and posterior) are somewhat flattened 

 when the viscus is empty, but rounded when it is distended : the parts in 

 contact with them have been referred to (p. 431). 



Borders. The upper border or small curve is concave towards the left 

 opening, but convex at the opposite end ; and the lower border or large 

 curve is convex, except near the right end, where it is concave the con- 

 cavity of the one border corresponding with the convexity of the other. 

 An arterial arch, and a fold of peritoneum (omentum) are fixed to each 

 border. 



STRUCTURE. In the wall of the stomach are four coats, viz., serous, 

 muscular, fibrous, and mucous ; and belonging to these there are vessels, 

 nerves, and lymphatics. 



Serous coat. The peritoneum gives a covering to the stomach, and is 

 adherent to the surface, except at each margin, where an interval exists 

 corresponding with the attachment of the small and large omentum : in 

 those spaces are contained the vessels, nerves, and lymphatics. During 

 distension of the stomach the spaces above mentioned are much di- 

 minished. 



The muscular coat will be laid bare by the removal of the serous cover- 

 ing. It consists of three sets of fibres longitudinal, circular, and oblique ; 

 these lie from without inwards in the order mentioned, and are unstriated 

 or involuntary. 



The longitudinal fibres (fig. 147, a) are derived from the oesophagus; 

 they spread over the surfaces, and are continued to the pylorus and the 

 small intestine. The fibres are most marked along the borders, particu- 

 larly at the smaller one; and at the pylorus they are stronger than in the 

 centre of the stomach. 



The circular fibres (fig. 147, b) form the middle stratum, and will be 

 best seen by removing the longitudinal fibres near the pylorus. They 

 reach from the left to the right end of the stomach ; but at the pylorus 

 they are most numerous and strongest, and form a ring or sphincter (c) 

 around the opening. 



The oblique fibres (fig. 147, e) are continuous with the circular or deep 

 layer of the oesophagus. On the left and right of the cardie orifice they 

 are so arranged as to form a kind of sphincter (d and e~) (Henle); but 



