THE FROG 97 



num, is bent forward so as to lie parallel with the stomach ; 

 between them lies the whitish, irregularly shaped pancreas. The 

 rectum is about half an inch long and forms the hinder part of the 

 intestine ; it is much wider than the small intestine and may often 

 be recognized by its dark color. The rectum is continuous pos- 

 teriorly with the cloaca,— a short, wide vessel which lies between 

 the base of the hind legs and finds an outlet through the anus. 



Observe again the extensive mesenteries which bind the divi- 

 sions of the digestive tract with the wall of the abdominal cavity. 



At one side of the forward portion of the rectum will be seen 

 a dark-red, spherical body, the spleen. Press the intestine and mes- 

 entery aside, but without cutting them, and observe the flattened, 

 dark-colored kidneys, which lie close to the dorsal body wall. At 

 their forward ends are the two yellow, spherical testes, if the ani- 

 mal is a male, or the irregular, saclike ovaries, if a female ; in front 

 of these organs are the yellow, finger-shaped fat bodies. 



Observe closely the liver and pancreas. The former is com- 

 posed of two main lobes, one of which is subdivided into two 

 smaller lobes. Note carefully the connection between these two 

 parts. Turn the whole liver forward,— but without cutting any- 

 thing,— pin it there, and study its dorsal surface and the pancreas. 



The pancreas is an irregular, whitish gland which lies in the 

 bend made by the stomach and the duodenum. Near the hinder 

 border of the liver note the spherical gall bladder. Find the bile 

 duct, which joins the liver with the duodenum. It is a slender 

 tube which issues from the gall bladder and, after receiving a 

 number of branch ducts from the liver, joins the duodenum a short 

 distance from the pylorus. It passes through the pancreas, from 

 which it receives one or more small pancreatic ducts. Gently 

 squeeze the gall bladder with forceps and force the dark-green bile 

 into the duct ; it will thus be easy to follow. If the bile will not 

 flow, cut the gall bladder open and inject a carmine solution or 

 India ink into it with a pipette. 



Exercise 6. Make a semidiagrammatic drawing of the dorsal surface 

 of the liver and pancreas, with an outline of the stomach and 

 duodenum, showing the features just described; carefully label 

 all the organs. 



