PREFACE TO THE SEVENTH GERMAN EDITION. 



THIS edition differs from the earlier ones by containing a new 

 chapter on " Physical Chemistry in Biology." This chapter has been 

 written by Professor S. G. HEDIN, of Upsala. In order to give space 

 for this new, second chapter, without changing the number of chapters 

 of the earlier editions, the fifth chapter of these earlier editions on " the 

 animal cell " has been dropped and its contents incorporated in the 

 other chapters. For example, in this edition the nucleic acids, as well 

 as the purine and pyrimidine bases, are treated of in connection with 

 the nucleoproteins, and the phosphatides are discussed with the fats in 

 Chapter V, a change which also seems necessary for other reasons. In 

 general, the plan of the book remains unchanged. The numerous publi- 

 cations in physiological chemistry which have appeared since the publica- 

 tion of the sixth edition have necessitated a thorough revision and 

 rewriting of all the chapters. Unfortunately a considerable increase in 

 the size of the book could not be prevented. 



OLOF HAMMARSTEN. 

 UPSALA, November 16, 1909. 



in 



