FROG 233 



the glottis ? To the lungs ? "What is the struct- 

 ure of its walls ? 



Cut away the anterior wall of the larynx and 

 note, leading to each lung, 



5. The bronchus. — What is the shape of the bron- 

 chus ? Length ? Structure ? 



c. The lungs. — "What position do the lungs occupy 



with regard to the larynx? The heart? The 

 liver? How are they held in place? "What is 

 the shape of the lung when collapsed? "When 

 distended ? How much larger than the former is 

 the latter ? "What is the texture of the wall of 

 the lung? On the distended lung look for the 

 ptilmonary artery, running the entire length 

 of the organ. Distend one of the lungs, then re- 

 move it by cutting through the bronchus, and 

 with a pair of fine scissors inserted into the 

 bronchial opening slit the lung along one side 

 to the end, and spread out the organ under water. 

 "What is the structure of the lung? Note the 

 network formed by muscles, connective tissue, 

 and blood-vessels. 



d. The vocal cords. — Open the glottis and look for 



two narrow bands of tissue stretched vertical^ 

 and running from before backward. 

 Make a diagram showing the arrangement of the res- 

 piratory organs. Draw a collapsed and a distended 

 lung to the same scale. Make a drawing showing a 

 cross-section of a distended lung; another drawing 

 showing the network on the interior. 



e. The vocal sacs. — Select a male frog and examine 



the vocal sacs. "What is their position ? Shape ? 



