24 THE FROG 



duct passes through it, and the pancreatic ducts empty into 

 the bile duct. Look up the course of the bile duct in the 

 human body; does it pass through the pancreas as in the 

 frog? 



3. The lungs, two thin-walled sacs lateral and posterior 

 to the heart; they lie dorsal to the liver and are usually 

 hidden by it. Insert a blow-pipe into the glottis of a freshly- 

 killed frog and inflate the lungs. 



4. The spleen, a round dark-red organ in the mesentery 

 near the anterior end of the large intestine. 



5. The excretory system, (a) The kidneys, a pair of 

 reddish, flat bodies lying next to the dorsal wall of the body, 

 and separated from the body cavity by a thin membrane, the 

 peritoneum. Expose a kidney by cutting through the peri- 

 toneum of one side only. If the specimen is a female, in 

 order to expose the kidney it may be necessary to remove 

 one ovary (described below) by cutting the membrane by 

 which it is attached. Observe a yellowish band, the adrenal 

 body, on the ventral surface of each kidney; this corre- 

 sponds to the suprarenal body of man. 



(b) The ureters emerge from the posterior fourth of 

 each kidney on its lateral edge. They are slender trans- 

 parent or whitish tubes, one for each kidney, which converge 

 as they pass posteriorly, and empty into the dorsal side of 

 the cloaca. 



(c) The bladder, a slightly bi-lobed sac opening by a 

 narrow neck into the ventral side of the cloaca. Insert a 

 blow-pipe or a large pipette through the anus of a freshly- 

 killed frog and inflate the bladder. 



6. The corpora adiposa, or fat bodies, yellow tufts of 

 flattened finger-shaped processes just anterior to the gonads 



