TRANSLATOR'S NOTE 



The translator has been associated with the author for three years 

 in experimental vitamine research, and it is a pleasure to record at 

 this point the spirit which animates him in his work and his earnest 

 desire to see real progress made towards the solution of the many 

 problems of nutrition. It was this which prompted the preparation 

 of the present edition, intended rather as a stimulus to thought and 

 further research than as an elaboration of technicalities. Inasmuch 

 as the author has had the opportunity of reading the manuscript 

 before it went to press, the reader may be sure that the sense of the 

 book has been accurately preserved. 



In conclusion, the undersigned wishes to extend his thanks to the 

 Hon. Herman A. Metz for the many facilities provided in the prepara- 

 tion of this book. 



HARRY E. DUBIN. 



Research Laboratory of H. A. Metz, 

 New York City. 



December, 1921. 



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