THE STOMACH 

 THE STOMACH 



239 



The stomach is apparently a new acquisition in the vertebrates, 

 possibly arising as a place for the storage of food. This view is sup- 

 ported by several facts. In the embryo vertebrate and in the adult of 

 Amphioxus the duct from the liver immediately follows the pharynx, 

 opening just behind the last gill cleft; while the innervation from the 



Fig. 253. — Different shapes of stomachs, mostly after Nuhn (Keibel). a,Belone;b, 

 Proteus; c, Tropidonotus natrix; d, Gobius; e, shark; f, Phoca vitulina; g, Polypterus; h, 

 Pulica atra; i, Tesludo graca; k, land tortoise; /, rabbit; m, pig; n, owl; 0, crocodile; p, 

 Delphinus; q, Halmaturus. 



tenth nerve shows that both stomach and oesophagus are parts of 

 the pharynx greatly drawn out (fig. 233). 



The pylorus, which limits the stomach behind, is a fold of the 

 lining mucous membrane projecting into the interior and reinforced 

 by a circular (sphincter) muscle, which by its contraction, closes the 

 tube so that no food can pass from the stomach until it is properly 

 acted upon by the gastric fluids. The anterior end of the stomach is 

 not so well marked. Usually it is differentiated from the oesophagus 



