PREFACE 



MOST adolescent boys and girls are more interested in themselves 

 than in abstract problems. Although colleges emphasize math- 

 ematics and languages in their entrance requirements and say little 

 about science, there has been a rapid growth in the number of 

 sciences elected in the high schools. This is primarily due to the 

 realization that science is more a part of the lives of pupils than 

 other school subjects and an answer to more of their questions. 

 Youth is more interested in making direct observations and reason- 

 ing from them than in abstract thinking. There is a concerted 

 effort to ascertain the truth about phenomena and to find out how 

 and why things happen. Science teaches a valid method of inter- 

 preting evidence and helps one to arrive at logical conclusions. 



In most secondary schools throughout the country elementary 

 biology or general science is taught in the first or second year. 

 There has been a growing demand for an advanced course in general 

 biology to follow the elementary science course. This text has been 

 written primarily to fill this need. The emphasis of the book is 

 on problems relating to human welfare. The origin and principles 

 of the development, structure, and functions of plants and lower 

 animals are introduced mainly as a background for the proper 

 understanding of human problems. 



An interesting and novel feature of the text is the historical 

 treatment of many of the subjects, which gives the pupil a bird's- 

 eye view of the entire subject without overwhelming him with 

 unrelated facts. Teaching material is given at the end of each 

 chapter, designed to help the pupil in organizing, in his own mind, 

 the important principles discussed. The list of supplementary 

 readings offers the pupil sources of information other than the 

 text. All the laboratory problems necessary for a thorough 



