VIU PREFACE 



dures and modifications which may confuse the uninitiated faced with 

 choosing among them— some degree of arVjitrary selection has been 

 employed. 



Chapter 6 presents in summary form a description of the characteristics 

 of each radioisotope sufficient to allow decisions as to suitable counting 

 methods, facilities required, and amounts of radioactivity to be employed. 

 Typical studies are presented, and where possible, details are given in 

 regard to those perversities which are so simple when explained but so 

 exasperating and time-consuming when unrecognized in the laboratory. 

 Chapters 7 to 10 describe the principles and application of corollary 

 technicjues that have been found of particular value in radioisotope 

 methodology. To avoid the inclusion of an overwhelming amount of 

 experimental detail, an attempt has been made first to present enough 

 information so that the investigator can determine whether or not a given 

 study is within his scope of facilities and experience. Frec^uently, suffi- 

 cient details have been given so that the procedures can be undertaken 

 without need for further reference. However, it is expected that most 

 often the reader will wish to consult the original literature for additional 

 information on specific methods. 



Obviously it was possible to refer to only a small proportion of the 

 literature, and the choice of material to be included was primarily based 

 on its suitability for the illustration of certain points. No attempt has 

 been made to discuss the status of knowledge in any scientific field as 

 correlated with radioisotope research; this falls more properly within the 

 purview of the Annual Revieio type of article. It is hoped that the illus- 

 trative examples vvill suggest the potentialities possible in the various 

 fields of research. Emphasis has been placed on the biological and prac- 

 tical aspects of the subject, with no discussion of electronic circuits and 

 with the inclusion of onh^ such mathematics and physics as are essential 

 to the methods. The interested investigator will want to develop his 

 background in nuclear physics and instrumentation from standard texts. 

 But let no biologist with training in quantitative chemistry be dis- 

 couraged from undertaking tracer studies, at least on a small scale. 



It is hoped that this book will provide stimulation for the biologist and 

 the agriculturalist who have not yet considered the use of radioisotopes, 

 as well as some degree of useful methodology for the investigator who is 

 already engaged in this field. If the physical scientist can gain from this 

 material an appreciation of the peculiar problems of his biologist colleague 

 as well as an urge to collaborate, this will be an added di\'idend. 



This opportunity is taken to acknowledge gratefully the enthusiastic 

 cooperation of the following individuals, who supplied unpublished data, 

 criticized parts of the manuscript, and made valuable suggestions: L. F. 

 Belanger, C. J. Collins, S. L. Hansard, S. L. Hood, P. M. Johnston, 



