vi PREFACE 



getting a fairly adequate idea of the whole life of any one 

 organism which is not attained by the usual course of a 

 study of types. 



In preparing this work it has cost much deliberation in 

 many cases to decide what material to include and what 

 to reject, and probably several things have been omitted 

 which it might have been desirable to have retained. The 

 literature dealing with the frog is almost appalling in its 

 extent. Perhaps no animal, except man, has been the 

 subject of so many scientific investigations. One seldom 

 picks up a volume of a physiological journal without find- 

 ing that the frog comes in for a share of attention in one 

 or more articles. It indeed seems, as is often remarked, 

 that the frog is especially designed as a subject for bio- 

 logical research. In fact, most of what is known in certain 

 departments of physiology is derived from a study of this 

 animal. 



The anatomy of the frog has been most exhaustively 

 treated in Gaupp's excellent revision of Ecker and Wie- 

 derscheim's " Anatomie des Frosches," and I am naturally 

 under great obligations to this work. Most of the state- 

 ments made in the present book regarding the anatomy 

 of the frog, however, I have verified by personal observa- 

 tion. Much of the material dealing with the physiology 

 and natural history of the frog is here brought together 

 for the first time. Where not otherwise mentioned, the 

 statements in this book are made with reference to the 

 common leopard frog of North America, Rana pipiens, 

 except in cases where they may be understood to apply 

 equally well to any species of the genus. 



