TRANSLATOR'S PREFACE 



Professor Michaelis's Wasserstoffionenkonzentration has become 

 well enough known during the past twelve years to my English speak- 

 ing fellow workers in the biological and related sciences to warrant 

 further introduction or any further statement of the reasons moti- 

 vating its translation into English, beyond the one of rendering this 

 book more available and useful to them. I am particularly gratified 

 in presenting this monograph with the additions covering the latest 

 developments which were so kindly prepared by Professor Michaelis 

 for this translation. I am greatly indebted to him for this and for 

 his interest and valuable suggestions. 



My further debt of gratitude is due to Dr. W. Mansfield Clark of 

 the United States Hygienic Laboratory of Washington for his ex- 

 tremely valuable criticism of the first draft of the manuscript; to 

 my colleague Dr. Arthur Grollman of The Johns Hopkins Medical 

 School for correcting the manuscript; to Dr. Irving H. Page of the 

 Cornell Medical College and to Dr. R. M. Ellsworth of The Johns 

 Hopkins Hospital for their generous help with the proofs; and to my 

 wife, Dr. Olga Marx Perlzweig for her most valuable aid in the fur- 

 nishing of adequate Enghsh equivalents for the more intricate Ger- 

 man constructions, and for constant help on all possible occasions. 

 To The Williams & Wilkins Company I express my appreciation of 

 their generous cooperation in seeing this volume through the press in 

 the most efficient manner. 



The Translator. 



Baltimore, June, 1926. 



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I 



library] a. 



IX 



