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PREFACE - 



This volume is intended as an introduction to the 

 elements of animal biology for the use of students in the 

 high school. The cut-and-dried method of exposition 

 which is so commonly found in text-books and which so 

 frequently deprives them of all traces of stimulating 

 quality has been avoided so far as was deemed compatible 

 with the presentation of such subject matter as a text-book 

 should contain. Although the book would best fulfil its 

 purpose if read in connection with laboratory work, I 

 have not included directions for such work, partly be- 

 cause it would add considerably to the bulk of the volume, 

 but chiefly because so many teachers nowadays prefer to 

 make laboratory outlines of their own. 



The order in which the main topics are treated is essen- 

 tially like that which is followed in several of the best 

 recent text-books. The general experience of teachers 

 of biology has shown it to be eminently desirable that the 

 student should possess a general knowledge of the animal 

 kingdom as a preparation for the study of physiology. 

 The section on the elements of physiology has therefore 

 been placed after the part devoted to a survey of the 

 principal groups of animals. Rather more than the 

 usual amount of attention is given to the role of bacteria 

 in causing disease, and to the way in which diseases are 

 spread and how they may be avoided. 



The third part of the book dealing with general topics 

 such as evolution, heredity and eugenics begins with a 



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