2 INTRODUCTION 



were introduced. Chemistry at that time con- 

 sisted of a large number of descriptions of known 

 substances and their use in the daily life, their 

 occurrence and their preparation in accordance with 

 the most reliable receipts, given by the foremost 

 masters of the hermetic {i.e. occult) art. 



In the same manner Biochemistry up to a quite 

 recent time consisted of a great number of descrip- 

 tions of different products accompanying living 

 organisms, their properties, use, and their composi- 

 tion, i.e. their content of hydrogen, oxygen, nitrogen, 

 sulphur, phosphorus or perhaps other elementary 

 substances. If possible this composition was ex- 

 pressed by means of a chemical formula. 



But even the quantitative element which is con- 

 tained in an analysis of the composition of a sub- 

 stance was lacking in cases where the substances 

 investigated occur in such small proportions that it is 

 not possible to isolate them in a pure form. We have 

 no other possibility of describing these substances 

 than by indication of their occurrence and mode 

 of preparation in the most concentrated and purest 

 possible form, with an indication of their character- 

 istic properties, unless we employ methods other 

 than those belonging to the old classical science 

 of Chemistry. Only by the use of the methods 

 introduced by the modern physical chemistry is it 

 possible to form an opinion of the manner in which 

 these substances react, and thereby to get a clear 

 scientific idea of their nature. The fundamental 

 fact must here be recalled that these substances 



