CHEMICAL FERMENTS. 577 



garded as proved when we have succeeded in separating 

 the active ferment from the hacteria. As a matter of isolation of 

 fact, the experiments which have heen made in this th 

 direction by Marcano and by Wortmann, have led to 

 an imperfect isolation of the ferment ; the former found 

 that the cultivating fluid filtered through porcelain, or 

 treated with chloroform, still showed a diastatic action ; 

 and Wortmann was able to demonstrate an isolated fer- 

 ment by extraction of the mixture of bacteria and pre- 

 cipitation with alcohol; this ferment was soluble in 

 water, converted starch energetically into glucose, acted 

 better in faintly acid solutions, and also exerted its 

 diastatic action when oxygen was excluded. Wortmann 

 found that this ferment was only produced by the 

 bacteria in question when they had at their command 

 neither albumen nor any other source of carbon ; 

 usually they furnished a peptonising ferment, but 

 instead of this they produced a diastatic ferment when 

 they were in a starving condition, and were unable to 

 obtain the necessary nutriment in any other way than 

 by solution of starch ; further, the ferment was only 

 formed when the bacteria had plenty of oxygen. Wort- 

 mann's observations are, however, not completely con- 

 vincing, because he worked with an unknown mixture of 

 bacteria, and also because the possible action of the 

 living bacteria, in addition to that of the supposed 

 isolated ferment, is not entirely excluded in the re- 

 searches, especially as the activity of the solution of the 

 ferment only appeared after a longish incubation period. 

 Nevertheless, taking into consideration all these experi- 

 ments, it is very probable that renewed experiments free 

 from these objections will lead to similar results as re- 

 gards the diastatic ferments of bacteria. 



2. Inverting ferments. These convert cane-sugar, invertin. 

 milk-sugar, and maltose into forms of glucose (dextrose, 

 laevulose, galactose). They occur in the digestive track 

 of animals, but they have not yet been demonstrated in 

 the higher plants. A similar ferment has, however, 

 been demonstrated by Gayon* in species of penicil- 



* Gayon, Bull. soc. ckim., 35, 58. 



37 



