206 THE FROG AS AN INTRODUCTION TO MAN 



2. Study a diagram of the respiratory organ of the frog, and 

 write a paragraph telling just how a frog gets air into and out 

 of its lungs. 



Observations. 1. Does the frog always remain entirely 

 under water ? If not, what part .of its head does it place out 

 of water ? Why ? 



2. Examine a dissected specimen or chart, showing bronchial 

 tube, trachea, and glottis. Insert a blowpipe in the glottis and 

 innate the lungs. Are they spongy ? Are they elastic ? 



Drawings (Optional) 



Draw a side view of the living frog, natural position. Label all parts 

 mentioned in the previous study. 



Questions 



1. What is the meaning of the term "Amphibia" ? 



2. Give the principal ways Amphibia may be useful to man. 



3. What becomes of frogs and toads in the winter ? 



4. Tell of metamorphism amongst the Amphibia. 



5. Why has the frog been used so much for dissection ? 



6. How does the food of larval and adult frogs differ ? How 

 do their digestive organs differ ? 



7. What are the principal enemies of frogs ? 



8. What is the truth about toads and warts ? 



9. Why should the toad be reckoned a good citizen ? 



10. How are the eggs of frogs protected from ravenous 

 fishes? 



References 



Hunter, Essentials of Biology. Chap. XXII. (Amphibia.) 



Elements of Biology. Chap. XXIII. 



" The Usefulness of the Toad." Farmers' Bulletin 196, U. S. Depart- 

 ment of Agriculture. 



Hodge, Nature Study and Life. Chap. XVI. 



Marshall, The Frog. 



Dickerson, M. C., The Frog Book. 



Workman, " The Toad as a Garden Benefactor." House and Garden 

 Magazine, March, 1910. 



