Preface to First Edition ^= 



Although the chemical nature of vitamins is still unknown much of 

 both scientific and practical importance has been learned regarding 

 them, and the present work is designed to summarize this knowledge in 

 as judicial a manner as possible. To those who "don't believe in vitamins 

 because we have never seen one" or who hold that we know nothing 

 about them chemically because no structural formula can yet be as- 

 signed, we would commend the view of Hopkins that it is easier to 

 sympathize with the farmer who will believe in vitamins only when 

 their price per hundredweight can be quoted in the market than with 

 the scientific man who refrains from an endeavor to appraise their 

 importance until they have been separated in pure condition. "To be 

 logical he should then avert his eyes from such agents as toxins and 

 antitoxins, not to speak of enzymes ; powerful realities all of them, 

 which though of unknown constitution by no means elude objective 

 and quantitative study." It is hoped that the present work may do 

 something to stimulate such quantitative research as distinguished from 

 the merely qualitative tests which have now largely served their pur- 

 pose, and at the same time may serve to present the chief facts now 

 known in such a way as to show their true significance and avoid exag- 

 gerated impressions. . . . 



The greater part of the text was written near the middle of the year 

 1921 but on a few points we have been able to bring our summary down 

 to about the end of that year, thus covering the work of the decade 

 since the term was introduced and the conception of the vitamins began 

 to be current. A carefully selected alphabetical bibliography of about 

 one thousand titles is included. Names and dates are so used in the 

 text that the reader may readily locate original places of publication by 

 turning to the bibliography, the need of footnote references being thus 

 avoided. It is hoped that this bibliography will suffice to put the reader 

 in touch with practically all of the more significant literature of the 

 vitamins to the end of 1921. The writers will be glad to be notified of 

 any serious omissions in case a second edition should be called for. 



