94 PHYSIOLOGY OF ALIMENTATION. 



theories of fermentation which have been proposed irom 

 time to time. Within the last few years, however, the work 

 which has been done on the so-called inorganic ferments 

 has so altered our older conceptions of the essential nature 

 of fermentation that a discussion of some of the analogies 

 between the organic and inorganic ferments may not be 

 amiss, even though the facts as they stand now have a 

 greater bearing on the theoretical than on the practical 

 side of the medical problems of fermentation. 



As early as 1863 SCHONBEIN pointed out the ana logy which 

 exists between the influence of finely divided metals (such 

 as platinum, iridium, silver) and that of a number of ferments 

 on the velocity of certain chemical reactions. The decom- 

 position of hydrogen peroxide, for instance, is accelerated 

 not only by the addition of aqueous extracts of various 

 animal and vegetable cells which contain ferments, but 

 also through the addition of the finely divided noble metals 

 mentioned above. The decomposition of hydrogen peroxide 

 occurs also in the absence of these substances, only then 

 much more slowly, so that the finely divided metals possess 

 the characteristic property of a ferment, namely, that of 

 altering the velocity of a reaction which occurs in its absence 

 also. 



Through the more recent work of BREDIG and with him 

 VON BERNECK, REINDERS, IKEDA, and the efforts of MC!NTOSH, 

 BILLITZER, NEILSON, and others, our knowledge of the inor- 

 ganic ferments has been greatly increased. For a fuller 

 account than can be given here and for references to the 

 literature the reader is referred to the monograph of BREDIG. 1 



In place of the coarsely powdered metals employed by 

 the older observers, BREDIG used so-called colloidal or pseudo- 

 solutions of these metals. The solutions are prepared by 

 sending an electric current through electrodes of the noble 



1 BREDIG: Anorganische Fermente, Leipzig, 1901; Ergebnisse d. 

 Physiologic, 1902, 1, Ite Abth., p. 134. 



