Youth is more interested in making direct observations and reasoning 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 interpreting 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.

The plan of – presenting the subject matter is based on the practical experience in teaching this course for several years to high school pupils by means of mimeographed lesson sheets prepared by various members of the Biology Department of the George Washington High School, New York, N. Y. Changes in these sheets have been made, but much of the material has been elaborated into the present text. The enthusiasm of the Biology Department in the George Washington High School is due largely to the inspiration and support of Harold S. Campbell, Associate Superintendent of the New York high schools. In his annual report of 1928 he included the report of the District Superintendent of High Schools, Dr. John L. Tildsley. In this report, Dr. Tildsley summarized thd objectives of science teaching and said:  

"These objectives call for the creation of a more magnificent self. They call for the expanding of the element of appreciation, the kindling of imagination, the arousing of the sense of admiration and wonder, the excitation of the emotions, the development of the power of accurate observation, the desire for truth, courage to follow the truth, and above all, the setting forth of science as 'a ' way of life.'"  

The authors hope this text will open this broader "way of life" and inspire pupils to think and to act magnificently.  

Thanks are due the Biological Supply Co., New York, for the use of photomicrographs prepared by Mr. Roy M. Allen, and also to Miss Marjorie Fitzpatrick, Mr. Charles Inman, and Mr. Paul B. Mann of New York city high schools, Prof. Ralph Cheney of Long Island University, and Miss Ada Weckel of Oak Park, Illinois, high school, for their critical reading of the manuscript.