PREFACE ix 



bring practical workers, whether chemists, physiologists, or technolo- 

 gists, into communication with the various authorities quoted. For 

 this reason full references have been given for every record of the 

 natural occurrence of the compounds and of the methods employed 

 for their synthetical production. As it has been found impossible to 

 read every paper in full in the original, it is also necessary to caution 

 those who use this volume that many of the papers contained in diffi- 

 cultly accessible publications have been seen only in the abstracts 

 published in the ' Chemisches Central-Blatt/ the ' Journal of the 

 Chemical Society,' the ' Journal of the Society of Chemical Industry,' 

 and in the ' Journal of the Federated Institutes of Brewing.' The 

 page given in the references must not therefore be quoted in all 

 cases without further verification as the actual page of the original 

 paper in which the statement occurs, but simply as a reference to 

 the page of the publication on which the original paper is to be 

 found. 



The vital products recognised in this volume are those compounds 

 of definite chemical composition which are known to be produced as 

 the result of the vital activities for the most part normal of animals 

 and plants, including of course the heterogeneous assemblage of micro- 

 organisms. As explained in the introductory chapter, considerable 

 latitude has been allowed in the interpretation of the term ' vital 

 product ' ; but it is to be understood that the syntheses of these 

 compounds as recorded are in every case complete in the chemical 

 sense. It is necessary to call attention to this point because in many 

 instances it may appear that where one vital product (X) has been re- 

 corded as a generator of other vital products (A, B, &c.), the compound 

 X having originally been synthesised from A or B, that we have got 

 out of X nothing more than was originally put into it, and that there 

 has accordingly been presented a case of ' circular reasoning,' or, in 

 other words, an incomplete synthesis. In all such cases, however, it 

 will be found that X can be obtained from generators other than A or 

 .B, and that the synthesis of X is therefore independently complete. 

 The importance of recording the inter-relations of X, A, and B is fully 

 explained in the subsequent pages. 



A compilation such as the present would have been for me an im- 

 possible undertaking without the free use of the standard works of 

 reference, and I must in the first place acknowledge my indebtedness 

 to Beilstein's ' Handbuch der organischen Chemie ' and its Supple- 

 ments ; to Watts's ' Dictionary of Chemistry,' Morley and Muir ; to 

 Thorpe's ' Dictionary of Applied Chemistry ' ; and to Eoscoe-Schor- 



