80 THE HUMAN BODY. 



pharynx, a canal with elastic walls formed by muscles, and 

 lined with mucous membrane. It extends from the back of 

 the mouth to the oesophagus, and is the vestibule of this 

 passage, a sort of funnel, the upper part of which shares in 

 deglutition, and adds to the resonance of the voice. The 

 anterior wall of the oesophagus is formed by the larynx, the 

 superior orifice of which, surmounted by the epiglottis, opens 

 into the pharyngeal cavity, so that it is only the half of a 

 canal completed in front by the larynx. 



The pharynx is continued below by the oesophagus, a tube 

 formed by two membranes, the external muscular and the 

 internal mucous. It is extensible and very contractile; it 

 descends between the spinal column and the trachea, which 

 it overlaps a little to the left, and on reaching the thorax it 

 follows the posterior mediastinum, and at last traverses the 

 diaphragm and opens into the stomach. 



The stomach. The form of the stomach has been com- 

 pared to that of a bagpipe. It is a large pouch, an expan- 

 sion of the digestive tube, placed transversely across the 

 upper portion of the abdomen. Its left extremity or great 

 cul-de-sac, lying in the hypochondriac region, is rounded and 

 larger than the right, which corresponds to the epigastrium. 

 Above, it forms a concave curve the lesser curvature; be- 

 low, a convex curve the greater curvature. The opening by 

 which it communicates with the oesophagus is to the right 

 of the great cul-de-sac, and is called the cardiac orifice; 

 and that which opens into the intestine, the pylorus, or pyloric 

 orifice. 



The walls of the stomach are formed of four membranes, 

 which, proceeding from without inwards, are a serous the 

 peritoneum a muscular, a fibrous, and a mucous membrane. 

 The muscular membrane is composed of three layers of 

 fibres, some longitudinal, others circular. These fibres are 

 slender and open for the most part, but near the pylorus 

 they are closer and stronger, and around this orifice they 

 form a muscular ring, which has been named the pyloric 

 valve. 



The intestinal canal is a continuation of the stomach; its 

 walls, like those of that organ, are composed of four mem- 



