vi Preface to the Second Edition 



matter, as a necessary first step in progress from the purely 

 empirical. From the methodical treatment of the subject-matter 

 under such heads as Hydrolysis, Oxidations, Ester formation, 

 and other special synthetic reactions a certain order has 

 been introduced, from which there result at least prominent 

 suggestions of the underlying constitutional relationships. 



So far has this proceeded that it is possible at this date to 

 propose constitutional formulae for even so complex a body 

 as a lignocellulose, such as would be a consistent summary of 

 the experimental facts as to composition and reactions. It 

 would, however, be premature to attempt this in any other 

 way than as a working hypothesis to guide investigations. 

 There remains, indeed, still unsolved the problem of the actual 

 condition of matter in these complex colloidal forms rela- 

 tively to the gaseous and liquid states, and pending a solution 

 of this major problem, we can only continue on the basis of 

 progressive empiricism which we originally adopted. 



The present is therefore in the main a reprint of the 

 former edition with a small portion of the text rewritten and 

 the addition of an appendix giving an account of more impor- 

 tant recent contributions. 



4 NEW COURT, LONDON, W.C. 

 February 25, 1903. 



