PREFACE 



These three volumes deal with the biological effects of radiations, 

 corpuscular and electromagnetic, throughout the energy spectrum from 

 the highest available energies to the near-infrared region. Radiation 

 biology has progressed through important stages during the last fifty 

 years. An upsurge of interest in the early years of the century was 

 stimulated by developments which followed the discovery of X rays and 

 radioactivity. In this era many of the fundamental phenomena in radia- 

 tion biology were recognized, during the early growth of concepts in 

 atomic and nuclear physics. Because much of the modern research had 

 its roots in investigations of this period, a study of these early reports is 

 still very rewarding. After World War I an important phase of research 

 was reached with the discovery of (1) the genetic effects of radiation in 

 Drosophila by Muller and, some time later, in maize by Stadler; (2) the 

 effect of density of ionization; and (3) the exact action spectrum of the 

 biological effects of ultraviolet. The unfolding of most of these early 

 investigations is discussed in B. M. Duggar's most comprehensive review, 

 "Biological Effects of Radiation." Significant aspects of radiation 

 biology have been discussed in Lea's book, "Actions of Radiations on 

 Living Cells"; the British Journal of Radiology supplement, "Certain 

 Aspects of the Action of Radiation on Living Cells"; the Oberlin sym- 

 posium on radiobiology, "The Basic Aspects of Radiation Effects on 

 Living Systems"; and many monographs. Modern developments in 

 biochemistry, biophysics, pathology, and related fields have established 

 a profound and growing influence on research in the radiation field. 



The discovery of the chain reaction in uranium initiated a new phase of 

 scientific endeavor. The phenomenon of nuclear fission has become a 

 practical instrument in the development of nuclear weapons ; it gives great 

 promise of becoming an economic factor as a power source; and it is 

 outstanding as a contributor of important research tools. Many of the 

 applications of nuclear energy are limited by their biological implications. 



These volumes grew out of a tentative plan to revise the Duggar 

 publication. However, the extraordinary expansion in radiation biology 

 made it desirable to go beyond a straight-line biological discussion and to 

 include in these volumes some discussions on the borderline subjects. 

 Important developments in the field of ultraviolet radiation, especially in 

 regard to its practical applications, justified extensive treatment. Wide- 

 spread advances in photosynthesis, photoperiodism, vision, and related 

 subjects demanded a complete volume on the effects of visible light. 



