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 ACKNOWLEDGMENTS \$ 3 



This book contains a slightly enlarged version of the material- 

 presented in a series of lectures given in the Department of 

 Zoology of the University of Chicago, in the spring of 1949, dur- 

 ing the tenure of a Rockefeller Fellowship. The main work of 

 preparing the manuscript was carried out at the Marine Biologi- 

 cal Laboratory, Woods Hole, during the tenure of a Lalor Fellow- 

 ship. 



It is a great pleasure to me to acknowledge my debt to Pro- 

 fessor Paul Weiss, who invited me to Chicago; to Professor 

 W. L. Doyle, who made the arrangements for my lectures; to 

 Professor P. B. Armstrong and his colleagues, who provided 

 such excellent facilities at Woods Hole. To the award of 

 Rockefeller and Lalor Fellowships I largely owe this opportunity 

 to crystallise the work on cytochemistry which has increasingly 

 occupied my attention since 1942. A number of immediate col- 

 leagues have worked together as a team, of whom I am particu- 

 larly indebted to Dr. I. J. Lorch and Dr. L. G. Bell. From 

 numerous other friends I have benefited by help and advice, in- 

 cluding particularly Dr. Honor B. Fell, Dr. E. Kodicek, Profes- 

 sor D. Keilin, Dr. H. Holter, Professor T. Caspersson, Professor 

 B. Commoner, Dr. A. E. Mirsky, and Dr. H. Jacoby. Facilities 

 for carrying out the researches reported here were provided Dy 

 Professor J. Gray at Cambridge, by Dr. F. S. Russell at the 

 Marine Biological Laboratory, Plymouth, and by Professor A. 

 Haddow at the Chester Beatty Research Institute, London. Dur- 

 ing the past three years spent .at King's College my group has 

 benefited by grants from the Nuffield Foundation, the British 

 Empire Cancer Campaign, and the Rockefeller Foundation. 



