A FROG 173 



The Digestive System {Continued). Dissect this system in the 

 following way. Lift up the liver with forceps, and with scissors 

 free its anterior border from the tissues beneath it, being careful 

 not to injure the lungs. Find the oesophagus, which joins the 

 stomach with the pharynx. Note that the lungs also join the 

 ventral wall of the pharynx. Take hold of the oesophagus with 

 forceps, lift it up, and with scissors cut across the floor of the 

 mouth in front of the lungs. 



The forward end of the digestive tract, with the lungs, being 

 thus cut loose from the body, can be bent backward. With scis- 

 sors cut the stomach and liver loose from the tissues beneath 

 them ; cut the mesentery by which the intestine is joined with 

 the dorsal body wall, being careful not to injure the flattened 

 kidneys and testes or ovaries, and straighten the intestine out. 

 The entire digestive tract, together with the lungs, will thus be 

 removed from the body, except at its hinder end. Extend it in 

 the water and pin it there, with the lungs attached to the phar- 

 ynx, and the liver and pancreas attached to the duodenum by 

 the bile duct. 



Exercise 8. Make a drawing of the digestive system, with the lungs ; 

 label all the parts and organs belonging to it. 



Slit open the stomach and the forward end of the intestine and 

 note the ridges on their inner surface. Cut open a lung and note 

 that it is a hollow sac with a network of ridges on the inner surface. 



The Urinogenital System. The urinary and the genital organs 

 are in close union with each other, notwithstanding their differ- 

 ence in function, and are conveniently studied together. The 

 urinary organs consist of the paired kidneys, the paired ureters, 

 the urinary bladder, and the cloaca. 



The kidneys are two large, flattened bodies which lie close 

 to the dorsal body wall in the posterior portion of the body 

 cavity. The ureter is a straight white tube which runs from 

 the outer posterior border of the kidney to the dorsal wall of 

 the cloaca. The urinary bladder is a large, bilobed sac at the 

 hinder end of the body cavity which springs from the ventral 

 wall of the cloaca. Its opening into the cloaca can be applied 



