22 THE FROG CHAP. 



gl. bt), the gall-bladder. In front of the liver and left 

 and right of the heart are two thin-walled, transparent 

 sacs (r. Ing, L Ing ) with a honeycombed surface, the lungs. 

 Their appearance varies very much according to their state 

 of distension. When full of air they are an inch or more in 

 length in a full-sized frog, and protrude freely as soon as 

 the abdomen is opened : when empty they hardly show 

 unless the liver is turned aside. 



Emerging from beneath the left lobe of the liver (beneath 

 in the present position of the animal, actually above) is a 

 wide, whitish tube (Fig. 3, .r/), which almost immediately 

 turns to the right (the frog's right, not yours), so as to 

 form a U-shaped bend (st, dm}. This is the stomach, 

 which is connected with the pharynx by a short tube 

 called the gullet or oesophagus (compare Fig. 7, gut, st), 

 and which varies considerably in size according to 

 whether it is empty or distended with food. The stomach 

 becomes continuous with a narrower tube, the first part of 

 which (dm} passes forwards parallel with the stomach, 

 thus forming the narrow limb of the U, while the rest of 

 it (s. int) is thrown into a rather complex coil. This 

 tube is the small intestine ; the part in immediate con- 

 nection with the stomach (dm) is distinguished as the 

 duodenum and the coiled part as the ileum. Between 

 the stomach and duodenum, in the bend of the U, is a 

 small yellowish-white body of irregular form, the pancreas 

 (Figs. 7 ,/, and 18, P). 



The stomach and intestine are kept in place and 

 suspended to the dorsal wall of the body-cavity by a delicate 

 membrane, the mesentery (Fig. 5, mes\ which is folded in 

 correspondence with the various coils. As we shall see, the 

 mesentery is really a portion of a thin, moist membrane, 

 the peritoneum, with which the body-cavity is lined. 



