A FROG 171 



tween 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 

 mesentery 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 animal 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 pan- 

 creas, 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 in 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 duo- 

 denum, showing the features just described ; carefully label all 

 the organs. 



