502 CONSTRUCTIVE AND DESTRUCTIVE METABOLISM 



of sugar, by finely divided platinum which acts as a vehicle for the 

 transmission of oxygen, and by finely divided iridium which induces the 

 decomposition of formic acid into hydrogen and carbon dioxide. Similarly 

 the formation of ether by the aid of sulphuric acid shows that katalytic 

 action may also induce molecular combination, and hence it is possible 

 that certain synthetic processes may be performed by means of enzymes. 

 It is, however, not always easy to determine whether or not a given change 

 is produced by a ferment, for many enzymes are extremely unstable, and 

 hence isolation is almost or entirely impossible. Moreover certain ferments 

 may exert a katalytic action only under the conditions presented in the 

 living and vitally active cell, so that the power of inducing fermentation 

 may in such cases be inhibited by anaesthetization with chloroform or 

 ether. On the other hand the possibility of such inhibition does not prove 

 that the alcoholic fermentation of sugar in a living yeast-cell may not be 

 due to the action of a ferment, indeed Buchner has recently succeeded in 

 isolating an alcohol-producing ferment from yeast 1 . Saccharomyces may, 

 however, still be termed a ' ferment-organism,' since the production of 

 ferment is due to the metabolic activity of the living yeast-cells. The term 

 ' ferment-organism ' is preferable to that of 'organized ' or ' formed ' ferment, 

 and the word 'enzyme' (Kiihne) or 'ferment' may be restricted to the 

 katalytic secretion of the ferment-organism. 



It is only recently that chemists have directed a proper amount of attention to 

 the long-neglected katalytic actions. The latter may be induced by organic as well 

 as by inorganic substances, and hence there is no reason for supposing that the 

 remarkable activity of ferments is due to the presence of minute fragments of 

 protoplasm. Ferments are to be regarded as stimulating or accelerating agents z t 

 and it is the task of physical chemistry to ascertain whether ferments are vehicles 

 for the transmission of special molecular movements, or act by means of the 

 dissociatory power of surface-tension energy, or by generating a series of actions 

 and reactions directed along particular channels. From a physiological point of 

 view we are concerned with facts only, and these teach us, for example, that 

 although sulphuric acid has theoretically an unlimited katalytic power, in actual 

 practice the latter is found to be strictly limited. The same is the case with 

 ferments; thus diastase is able to hydrolyze 10,000 times its own bulk of starch, 

 while invertin can invert 100,000 times its own volume of cane-sugar 3 . Since 



1 E, Buchner, Ber. d. Chem. Ges., 1897, pp. 117, uoo. [Cf. also Green, Rep. Brit. Ass., 1898 

 (Botany) ; Nature, September, 1898.] 



1 See Ostwald, Ber. d. Sachs. Ges. d. Wiss., 1894, p. 337. For older speculations, see Ad. Mayer, 

 Lehre v. d. chem. Fermenten, 1882, p. 104; Handb. d. Chem., Bd. IV, p. 124; Bunge, Physiol. 

 Chemie, 1894, 3. Aufl., p. 168. 



* Schleichert, Die diastat. Fermente d. Pflanzen, 1893, p. 85; Invertin, O. Sullivan and 

 Thompson, Koch's Jahresb. d. Gahrungsorg., 1890, p. 171 ; A. Meyer, Unters. iiber die Starkekorner, 

 J 895, p. 67. On the alteration and wearing out of enzymes, cf. Tammann, Zeitschr. f. physiol. Chemie, 

 1895, Bd. xvm, p. 427. 



