CHAPTER IV 



STRUCTURE AND LIFE OF AN ANIMAL (FROG) : AN 

 INTRODUCTION TO ANIMAL BIOLOGY* 



32. Why the Frog is selected for Study. Other ani- 

 mals might serve as types for this study; but it is better 

 to select a backboned or vertebrate animal, because such 

 an animal, by reason of its great similarity to human structure 

 and functions, will make it easier to apply this introductory 

 study to later lessons on human biology. And among the 

 backboned animals none has been so popular for scientific 

 study as the common frog. Many books, some of them 

 very large, have been written about the biology of this animal, 

 and the scientific knowledge concerning it is greater than 

 that on any other animal. Strange as it may seem, we know 

 far less concerning the human body from direct study; 

 but fortunately the frog and the human are so much alike 

 in numerous ways that biologists have applied to the human 

 species many facts which were learned first by study of the 

 frog. Since the study of the frog by scientific men has played 

 so important a part in building up the science of animal 

 ]biology } teachers now regard this animal as valuable for 

 study by those who wish to rediscover for themselves some 

 of the most important facts concerning animal structure and 

 life. 



The common green frog is usually most available for 

 -study, but the descriptions which follow will fit any other 

 species of frog, or even the common garden toad. 



* To THE TEACHER : This chapter may be studied after the lessons on the 

 plant, Chapter V. See note in Chapter IV in " Teachers' Manual." 



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