TRE COMMON FROG. 



their ears ? What effects result from all kinds of 

 local irritations, from chokings, from poisonings, from 

 mutilations the most varied ? These are the questions 

 again and again addressed to the little animal which, 

 perhaps more than any other, deserves the title of 

 "the Martyr of Science." 



To return to our question at starting, " What is a 

 Frog ? " 



To answer this, it will in the first place be well 

 to make a certain preliminary acquaintance with the 

 Frog absolutely. 



Secondly, to study those creatures which are most 

 like it, and are, therefore, as we shall directly see, its 

 "class fellows," living and fossil. 



Thirdly, to investigate its anatomy so far as to 

 be able to institute fruitful comparisons, between its 

 organisation and that of all other creatures belonging 

 to the same great primary group of animals to which 

 it pertains. 



Fourthly, to sum up the results in a series of suc- 

 cessively wider and wider comparisons, and by the 

 light thence derived to answer as fully as the present 

 state of Science allows the question first asked. 



We shall then be able to answer that question, 

 because we shall have ascertained how various parts 

 of this creature form one organic whole as a system 

 of mutually related structures ; and how this whole 

 and its parts are related to the entire series of 

 animal existences from the monad up to man. Then, 

 and then only, shall we be able to say what a 

 Frog is. 



In the first place it is necessary to acquire a general 



