PREFACE 



A scientist invited to deliver a series of lectures has first to select a 

 theme which is determined essentially by his own field of interest 

 and activity. The scientist then has to organize the lectures according 

 to the interest and knowledge of the potential audience. This is 

 especially important when a biologist is going to lecture in an in- 

 stitute of technology, despite the fact that this institute enjoys an 

 excellent department of biology. The Compton Lectures, as I was 

 told, are intended for a very large group of students, mostly physi- 

 cists and chemists. After discussing this matter with my M.I.T. 

 colleagues, I decided that these Compton Lectures would be directed 

 toward the young physicists and chemists, with a very specific goal, 

 namely to interest them in biological problems. It is in view of this 

 ambitious aim that biological order was selected as a theme. The 

 lectures, being intended for physicists and chemists, were planned 

 as if the audience knew nothing about biology. I certainly have to 

 apologize for this hypothesis. 



Thus life, the organism, and the cell have been defined and the 

 problem of biological order posed in its generality. VVe have dis- 

 cussed in succession: the hereditary order, namely the nature, struc- 

 ture, reproduction, and variation of the genetic material; the 

 functional order, namely the control of enzyme synthesis, and the 

 interaction of heredity and environment; and finally viruses as 

 representative of a specific order and at the same time of disorder. 

 Biological order has been considered at the molecular level in its 

 static as well as in its dynamic aspects. I have tried to explain how 



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