224 COMPARATIVE MORPHOLOGY OF VERTEBRATES. 
cesophagus usually extends a short distance into the body cavity and 
then its lower end has the same coat. 
The true stomach is characterized by the presence of glands, de- 
veloped from the mucous layer and emptying into the lumen. Of 
these glands there are at most (mammals) three kinds: cardiac, near 
the entrance of the cesophagus, which secrete an albuminoid fluid; 
Pm 
is) 
Fic. 227.—Different shapes of stomachs, mostly after Nuhn (Keibel). a, Belone; 6, 
Proteus; c, Tropidonotus natrix; d, Gobius; e, shark; f, Phoca vitulina; g, Polypterus; h, 
Fulica atra; i, Testudo greca; k, land tortoise; 1, rabbit; m, pig; 2, owl; 0, crocodile; p, 
Delphinus; q, Halmaturus. 
pyloric, near the pylorus, which form mucus; and the most character- 
istic, the fundus glands, which secrete a digestive ferment, pepsin. 
(For the structure of these glands reference should be made to histological 
text-books.) Tested by glands, many vertebrates (dipnoi, cyprinoids) 
lack a true stomach, while the sturgeons have the gastric glands extend- 
ing into the cesophagus. On the other hand, a part of the enlargement 
called the stomach in mammals often includes a part of the cesophagus 
(fig. 228, A, Z). 
