BARRY COMMONER 377 



biochemical process. This problem is familiar to biologists, and the 

 solution — the use of highly specialized cells as objects of study — is 

 equally Avell known. The discovery of the highly specific ESR signal 

 due to a photosynthetic free radical component (II) which is readily 

 identifiable in isolated chloroplasts and in whole living algae is addi- 

 tional evidence of the usefulness of this biological principle. 



The dependence of ESR studies of biological systems on principles 

 of physics, chemistry, and biology is also exemplified by the great debt 

 which this ^vork owes to the efforts of my colleagties Professor Jonathan 

 Townsend of the Department of Physics and Professor S. I. Weissman 

 of the Department of Chemistry. 



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