366 



THE FROG. PHYLUM CHORDATA 



DIGESTION 



The food is not chewed, but is swallowed whole, the only use 

 of the teeth being to prevent the escape of the prey, which they 

 can the better do because they slant backwards. Digestion 

 follows the same general course as in the mammal (p. 444)- 

 Pepsin, however, is produced by the oesophagus as well as by the 



cm. 



g gjh - ' S^mft r^- — ^ ~ '" "Z. '"*- — TT- 



r 



J R'o-iAj^' j y^'- jgfeL^ JiyJ^-^..^,^:-^ 





X/.^. 



Fig. 283. — A portion of the section shown in Fig. 282, more highly magnified. 



b.v., Blood vessel; c.t., connective tissue of mucous membrane; cm., circular layer of muscle fibres; 

 ep„ epithelium ; g.c, goblet cell ; let., ' lacteal ' or lymph vessel of the intestine ; leu., leucocyte of 

 lymph or lymph corpuscle ; m., longitudinal layer of muscle fibres ; p.e., peritoneal epithelium. 



stomach, the secretion of which is not so acid as in man ; in it 

 the food remains for from one to three days. 



In the liver a part of the excess of carbohydrate and fatty 

 food taken during the summer is stored for use during the winter 

 sleep and the breeding season. The fat is stored in droplets, 

 the carbohydrate in the form of glycogen or animal starch, which, 

 when it is to be transferred to other parts of the body, is converted 



