508 SPECIAL PHYSIOLOGY. 



terior surfaces of the organ. At the oesophageal opening, they form 

 the so-called stellate fibres, and, at the pylorus, they are again dis- 

 posed in a uniform layer, and become continuous with the longitudinal 

 fibres of the small intestine. The circular fibres, internal to the lon- 

 gitudinal ones, form thin circular fasciculi at the great cul-de-sac, and 

 surround the whole extent of the stomach up to the pyloric end, where 

 they are collected into a dense ring, which projects inwards, and forms 

 an annular sphincter muscle. This projecting ring, covered, on its 



Fig. 88. 



Fig. 88. Vertical section throngh the pyloric end of the stomach, and the curved part of the duodenum, 

 to show the circular fold, or annular valve, at the pylorus, s, small part of the stomach, d, part of the 

 duodenum, p, the pylorus, or pyloric opening of the stomach, with its annular valves, a, ends of the 

 common bile duct, and the hepatic duct, entering the left side of the bend of the duodenum, to open 

 internally by a common orifice. Much reduced in size. 



interior, by the mucous membrane, constitutes the pylorus or pyloric 

 valve (nuty, agate), Fig. 88,/>, the muscular fibres of which can partially, 

 or completely, close the pyloric aperture of the stomach. The oblique 

 muscular fibres do not, like the longitudinal and circular set, to which 

 they are internal, extend over all parts of the stomach ; from around 

 the oesophageal opening, where they are continuous with the circular 

 fibres of the oesophagus, and form a sort of sphincter, they may be 

 followed for a short distance on the great cul-de-sac of the stomach,- 

 spreading obliquely downwards on its anterior and posterior surfaces. 

 The muscular fibres of the stomach are pale, and, for the most part, 

 non-striated, though a few, in the longitudinal layer, present traces of 

 indistinct striae. 



The areolar coat of the stomach, sometimes called, from its position, 

 the submucous coat, consists of dense areolar tissue, containing some 

 fatty tissue, and a delicate layer of unstriped muscular fibres. It 

 supports the mucous coat, and, like it, is of greater extent, and less 

 expansible, than the muscular and serous coats; with the muscular 

 coat it is connected by very loose areolar tissue, so that in the empty 

 condition of the stomach it is thrown, together with the mucous mem- 

 brane, into numerous irregular, but chiefly longitudinal, folds, called 

 rugce. The bloodvessels, lymphatics, and nerves, belonging to the 

 mucous coat, subdivide in the areolar coat, before they enter the mu- 

 cous membrane. From the number of vessels in it, the areolar tunic 

 was formerly named the vascular coat, and from its white color, the 

 nervous coat; both terms, however, are objectionable. Its muscular 



