X PREFACE 



Coulter, L. G. Gillespie, E. G. Hastings, H. R. Thornton, 

 and R. W. G. Wyckoff, for permission to use some of their 

 graphs. 



Finally, I wish to express my special gratitude to the 

 publisher who undertook the printing of this textbook, 

 because he had the confidence that the book will have 

 its place in bacteriological and biological literature. 



Otto Rahn. 



Ithaca, New York. 



