( 20) 



maltextract or glucose broth, — does not at all decompose hydrogen 

 superoxyd. 



If we consider how generally catalase is met with in the animal 

 and vegetable kingdom, as also in the microbes, its very absence in 

 the lactic, ferments appears in a peculiar light. 



All active lactic acid ferments from milk invert sugar (invertase 

 reaction) and can more or less easily decompose esculine and indican 

 (emulsine reaction). The reaction on esculine is demonstrated by 

 introducing, for example, 0.1°/, of this substance and a few drops 

 of ferricitrate solution into whey agar or whey gelatin. Streaks drawn 

 on it of species which decompose esculine produce intensely brown 

 or black diffusion (ields of esculetiniron, brown at more alcaline, 

 black at more acid reaction, so that the lactic acid ferments become 

 recognisable by the black fields in the midst of which their colonies 

 are placed '). So long as esculine is present it is recognised by the 

 magnificent blue fluorescence of the whole plate at feeble alcaline 

 reaction. Indican may be used in a corresponding way but then no 

 iron salt is wanted as the indoxyl produced from the glucosid 

 oxidises of itself at the air to indigo blue. The lactic acid ferments 

 decompose these two glucosides, slowly indeed, yet these reactions 

 are very characteristic and useful. Amygdaline is not decomposed by 

 the lactic acid ferments. 8 ) 



To the most remarkable properties of the lactic acid ferments 

 belongs their power of reducing levulose to mannite, 3 ) which latter 

 substance may even in concentrated nutrient solutions be recognised 

 by its ready cristallisation at evaporation. A single drop dried on 

 the object glass, commonly gives at microscopical investigation full 

 certainty as to the existence of this reaction. 



The lactic acid ferments thereby strongly contrast with the so 

 nearly allied vinegar bacteria, in as much as the latter do just the 

 reverse, i. e. they change by oxidation mannite into levulose. 



Like so many other bacteria the lactic acid ferments possess, 

 also with regard to various pigments, a strongly reducing power, 



!) The knowledge of this extremely sensitive reaction, which has been applied 

 for years in my laboratory, I owe to my colleague Mr. H. ter Meulen. 



a ) Amygdalin is decomposed with much more difficulty by the action of microbes 

 in general than the other glucosides named in the text. Moulds mostly decompose 

 it into amygdalinate of amonium ; beer yeast into amygdalonitril glucosid and 

 glucose. Splitting under production of bitter almond oil, hydrocyanic acid and glucose 

 I detected hitherto only with Saccharomyces apiculatus and with the anaerobic 

 ferment of butyric acid fermentation, Granulobacter saccharobutyricum. 



3 ) Ferments lactiques de l'industrie. Archives Néerlandaises 1901. Kayser, Fer- 

 mentation lactique. Annales de l'Institut agronomique 1904. 



