I.] THE FROG. 47 



(S. Its lining inejnbrane; smooth and comparatively 

 thin. 



3. The liver, bile and pancreatic ducts. Cf. Sect. B. 2. a. 

 Gently squeeze the gall-bladder between the finger 

 and thumb of the left hand, keeping your attention 

 fixed on the duodenum and pancreas. The bile- 

 duct will be thereby injected and the bile will be 

 seen to enter the duodenum by a small orifice 

 situated at about its middle. 



a. The common bile-duct; its terminal third is plainly 

 visible, as a delicate tube (now injected green) 

 emerging from the pancreas to enter the duode- 

 num. Follow it up; it runs through the pancreas 

 towards the gall-bladder. 



b. The hepatic ducts ; variable in number. Seen, on 

 moving the gall-bladder about, to pass from the 

 liver and unite to form the main duct a'. 



c. The gall bladder ; a blind sac, set on at the ex- 

 treme end of the above system of ducts. Open it, 

 and note that it communicates with the liver 

 through the agency of the hepatic ducts alone. 



d. The pancreatic ducts; one or more in number; 

 seen, on careful examination, to enter the bile- 

 duct as it courses through the pancreas. 



4. The cloaca and bladder. Cut away the front of the 

 pelvis with a stout pair of scissors, taking care not to 

 injure the bladder: remove the front wall of the 

 latter, together with a portion of that of the large 

 intestine. Pin the bladder aside and examine under 

 water. 



a. The cloaca; the terminal portion of the alimentary 



