PREFACE 



This text is the outcome of a course of lectures given 

 to Lower Division students at Stanford University in 

 satisfaction of one of their requirements. The course 

 has been conducted by a committee with the assistance 

 of a number of their colleagues, acknowledgment of which 

 is made below. 



The idea underlying this book which was adopted by 

 this committee has been set forth at some length by 

 Professors Burlingame and Martin in Science for May 

 7, 1920. The idea is substantially this. Biology has now 

 reached such development that it comprises a large 

 amount of information and knowledge which is not 

 only of the first practical importance to the layman 

 but is also susceptible of being organized into a 

 coherent set of principles suitable for presentation to 

 the ordinary freshman or to the lay public. This 

 necessarily involves stressing principles rather than 

 factual details and limits discussion to such topics as do 

 not put an undue strain on the reader's knowledge of 

 related sciences such as physics, chemistry, and geology. 



An inspection of the table of contents will show that 

 the thread which runs through the whole is the inter- 

 dependence of organisms, especially in relation to man. 

 This it seems to us naturally involves a discussion of the 

 following topics at least: 



I. The nature of the living substance, protoplasm, and 

 its division and differentiation into the specialized cells 

 of complex organisms. 



II. The role of green plants in the synthesis of the 

 primary food and fuel compounds as a source of material 

 and energy for all living things. 



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