AMPHIBIA. 191 



while the rest is thrown into several coils. Its lining is raised 

 into transverse folds connected by fainter longitudinal ridges. 

 The end of the small intestine suddenly dilates into a short 

 thin-walled large intestine, which narrows behind and becomes 

 continuous with a chamber, the cloaca, opening externally by 

 the small circular doacal aperture. The cavity of the large 

 intestine is separated by an annular valve from that of the 

 small. Its lining is at first raised into delicate intersecting 

 ridges, and then into longitudinal folds which pass back to the 

 end of the cloaca, the posterior part of which is lined by ordinary 

 skin. 



Two important glands are connected with the alimentary 

 canal the liver, and pancreas. 



The liver is a very large reddish-brown organ, occupying a 

 considerable space near the front of the body-cavity. It arises 

 as an outgrowth from the alimentary canal, which quickly be- 

 comes bilobed. In accordance with this the adult liver is divided 

 into right and left halves, connected by a narrow strip of liver- 

 substance. The left half is again subdivided into two, so that 

 altogether three lobes are present. These are convex ventrally, 

 somewhat concave dorsally, blunt-ended in front, and elsewhere 

 thinning oft* into edges. The liver secretes the bile, a bright 

 yellowish-green fluid. Closely attached to the dorsal surface of 

 the right lobe is a rounded thin-walled sac, the gall-bladder, full 

 of bile, in the fresh state. From it a short tube, the cystic duct, 

 proceeds, which is connected with a fine network of hepatic ducts, 

 arising from the liver. From this a bile-duct is given off, which 

 is reinforced by other hepatic ducts, and runs in the U formed 

 by stomach and duodenum, finally opening into the latter about 

 half an inch beyond the pylorus on the inside of the U. 



The pancreas is an elongated yellowish mass lying in the 

 U-shaped loop, and produced into several tapering processes. 

 With it the bile duct is closely connected, receiving from it a 

 number of small pancreatic ducts. This gland secretes the pan- 

 rreatic juice. 



The digestive and other organs of the frog are contained in 

 the large pleuro-peritoneal- or "body-cavity (coelom). This 

 narrows in front, where it is bounded by the heart in its 

 pericardium, and a kind of muscular partition, the diaphragm,. 

 It also narrows behind. Its dorsal wall is formed bv the back- 



