FOREWORD 



The advent of the cyclotron and the nuclear reacting pile has heralded 

 what may be regarded, when viewed by future historians, as the beginning 

 of an entirely new and spectacularly successful era of scientific development. 

 For the physicist, high-energy accelerators have provided the means for 

 unraveling the next and, as yet, the most difficult phase in our progressive 

 understanding of the actual nature of matter. They have made the nucleus 

 accessible to investigation in much the same way that the optical spectro- 

 graph permitted an exhaustive study of the atom. The impact of radio- 

 active materials and the half-dozen readily available nuclear radiations on 

 medical research and the biological sciences has been no less profound than 

 for the physical sciences. The rapidly developing tracer techniques have 

 provided a research tool whose power of analysis has only begun to be fully 

 utilized in biology. Although only a few' isotopes and nuclear radiations 

 have as yet found a justifiable place in medical investigation, it is difficult 

 at present to predict the medical applications that doubtless will be developed. 



In some respects, one of the important results of the development of 

 artificial radioactivity has been the dissolution of the remaining barriers 

 between the biological and physical sciences. Serious students of physics 

 have now found a real challenge in the problems of biology and medicine. 

 They are joining with the biologist in increasing numbers to form efficient 

 research teams with virtually no limits to the fields of experience and knowl- 

 edge from which they can draw. This book is an example of the concerted 

 effort of physicists, biologists, and chemists. The data and the physical 

 principles and methods so necessary to the intelligent use of tracers and 

 nuclear radiations are to be found for the most part only in the literature of 

 the physical sciences. In that form it is almost inaccessible to the biologist, 

 and it is often inconveniently scattered for the physicist. With this problem 

 in mind, the present volume was prepared in an effort to present the necessary 

 data and methods in compact form. Having observed with considerable 

 interest the development of the book from its beginnings, I feel certain it 

 will serve an important function in supplementing the combined experience 

 of research groups by providing a long needed technical reference. For 

 those persons yet unfamiliar with the physical and biological literature in 

 this field, it would appear to provide much of the fundamental material 

 with which he must familiarize himself before attempting intelligent and 

 useful investigations with isotopic tracers and nuclear radiations. 



John H. Lawrence 



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