FOREWORD 



MANY diagnostic and therapeutic procedures in medicine 

 and surgery are based upon the elementary principles of 

 physics. We have become so accustomed to accepting and 

 utilizing these procedures in the everyday pursuit of our voca- 

 tions that we have oftentimes neglected to pause and give 

 thought to their origin. The present volume admirably em- 

 phasizes our obligation to fundamental science. 



The radiologist, the radiation biologist, and the physiologist 

 have of necessity been more closely associated with the physicist 

 than have many of their colleagues. This association in conjunc- 

 tion with the biochemist has resulted in the development of the 

 specialty known as biophysics which has been a major contribu- 

 tion to the advancement of the medical and biological sciences. 

 This specialty is rapidly expanding in influence and usefulness. 

 The biophysicist is frequently a catalytic agent, facilitating the 

 successful progress of a coordinated research program. 



The pile production of large quantities of radioactive isotopes 

 and their distribution to competent investigators by the Atomic 

 Energy Commission have stimulated research groups to redouble 

 their efforts toward the solution of many complex biological 

 problems. There is a notable tendency to coordinate the talents 

 of many investigators, each specialized in his particular field, 

 toward the solution of a specific problem. In such cooperative 

 work it is particularly important that each worker's specialty be 

 intelligibly presented for the illumination of his fellow workers 

 as is done by the present volume. 



The biological effects of penetrating radiations have been of 

 the utmost interest to many investigators and clinicians since 

 the discovery of X-rays by Roentgen in 1895 ; yet our knowledge 

 concerning the actual mechanisms of the biological actions re- 



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