152 



THE BIOLOGY OF THE FROG 



CHAP. 



peptones. The latter differs from pepsin in that it acts in an 

 alkaline or neutral medium ; in a strongly acid medium its 

 action is entirely stopped. 



The Liver. — The liver' is a massive gland whose secre- 

 tion, the bile, is conveyed to the intestine through the bile 



duct along with the 

 fluid secreted by the 

 pancreas. The or- 

 gan is of a dark red- 

 dish color, and is 

 divided into a right, 

 a left, and a middle 

 lobe. The middle lobe 

 is small and con- 

 cealed from view by 

 the heart. The left 

 lobe is divided by an 

 oblique incision into 

 an anterior and a pos- 

 terior portion, the lat- 

 ter occupying the 

 middle of the poste- 

 rior part of the liver. 

 The greater por- 

 tion of the liver is 

 covered by a closely 

 adherent layer of per- 

 itoneum, which is 

 continued to form at- 

 tachments with t h e 

 pericardium, ventral 

 body wall, dorsal body wall, and the stomach and intestine. 

 The bile duct is formed by the confluence of the hepatic 



FlG. 42. — Liver and pancreas of frog. Dc, 

 common bile duct; Dcy, cystic ducts; DA, 

 DA 1 , hepatic ducts, which with the cystic 

 ducts combine to form the common bile 

 duct; G, gall bladder; L, L\ LP, D\ lobes 

 of the liver turned forwards ; Lhp, hepato- 

 duodenal ligament; M, stomach; P, pan- 

 creas ; P 1 , pancreatic ducts entering the 

 common bile duct; Py, pylorus. (After 



• Wiedersheim.) 



