PREFACE 



THE present book is the outgrowth of a course of 

 lectures delivered during the past six years at the Uni- 

 versity of Michigan. This course with the accompanying 

 laboratory work was based on the frog, which was chosen 

 as a convenient form with which to introduce students to 

 a knowledge of the morphology, physiology, and life his- 

 tory of vertebrate animals. In writing this book I have 

 had in mind the needs of students, such as most of those 

 taking this course, who have had some preliminary work 

 in general biology, but who have forgotten most of what 

 little of the elements of physiology they may have learned 

 in the schools. A certain amount of physiology of a more 

 or less general nature has accordingly been introduced in 

 addition to the descriptions of the special functions of the 

 various organs of the body. The book is more suitable 

 for use as a text in college or university classes than in 

 high schools, although it is hoped that it will prove of 

 service to teachers in high schools where the frog is 

 studied in the course in zoology. 



Considerable space has been devoted to describing the 

 habits and natural history of the frog, and the endeavor 

 has been made throughout the work to correlate the study 

 of structure with that of the physiological functions of the 

 body and the activities of the organism as a whole in rela- 

 tion to the environment. There is, I believe, a value in 



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