PREFACE TO THE SECOND EDITION 



This edition, totally revised and almost completely re-written, 

 appears seven years after the first edition, deferred because of the 

 World War. In the interim, we have received many communications 

 from our colleagues informing us that our effort had provided them 

 with a welcome stimulus to their work. We have watched the great 

 development of this field of research since the appearance of The 

 Vitamines and it is a source of great pleasure that our work has also 

 contributed to this progress. The views expressed at the time have 

 been tested, for the most part, and found correct. While the first 

 edition was published at a time when great differences of opinion 

 prevailed, our desire then being to take cognizance of all of them, we 

 feel justified now in reviewing only those investigations, the view- 

 point of which is not too far removed from ours. In this way, it 

 has been possible to make the book more comprehensive. The 

 subject of vitamines, already beyond the stage of hypothesis, is based 

 on a firm foundation and has received universal recognition. In 

 spite of this, however, we are well aware that great gaps exist in our 

 knowledge, so that we can not regard the chapter as closed. 



These gaps may be explained by the fact that the field of vitamine 

 research gave many investigators the opportunity of making a name 

 for themselves with rather superficial work. Only seldom did they 

 seriously endeavor to get at the basis of the phenomena observed. 

 To permit of progress in the subject of vitamines, it would be very 

 desirable that at least some of the workers should abandon the beaten 

 path of exclusive animal experiments and break a fresh trail leading 

 towards the chemistry, physiology and pharmacology of the vitam- 

 ines, as well as the anatomical pathology of the avitaminoses. 



For help in the preparation of this edition, we are indebted to 

 many of our colleagues; we wish also to express our thanks to the 

 Medical Research Committee (London) and to Dr. Alfred F. Hess 

 (New York) for permission to reproduce a number of illustrations. 

 In addition, we wish to thank those whose permission it was impos- 

 sible to obtain because of uncontrollable circumstances. We are 

 especially grateful to Dr. Richard Hamburger, First Assistant at the 

 Pediatric Clinic, Berlin, who took it upon himself to correct and 



critically review the proofs. 



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