274 BACTERIA IN THE MANUFACTURE OF SUGAR. 



the explanation of which is clear : the outer layer of the cell 

 membrane swells up, detaches itself, and now encloses the cell on 

 all sides, so that when this process has been repeated several 

 times the envelope continually increases in size, whilst the dimen- 

 sions of the bacterial cell itself remain unaltered. By softly 

 pressing the cover-glass of such a zooglcea preparation the cells 

 can be forced out of their mucinous envelopes. 



As already remarked, the substance of which this envelope con- 

 sists was stated by Scheibler to be dextran, an opinion also shared 

 (as the result of analytical experiments) by P. DAEUMIGHEN (I.). 

 If, however, we consider the means by which these chemists 

 arrived at their discoveries, doubts will arise as to the accuracy of 

 their conclusions. In all attempts, made by macrochemical means, 

 to determine the composition of the vegetable cell membrane, the 

 same difficulty is encountered, viz., the solution and removal of 

 the cell contents. In order to attain their object, the reagents 

 employed for this purpose must penetrate through the cell- wall, 

 and since they come into contact with it whilst still in all their 

 pristine strength, they decompose it more or less effectually. When 

 the lixiviation of the cell contents is completed, then the pro- 

 duct remaining behind for ultimate analysis cannot be considered, 

 in point of composition, as unaltered cell-membrane substance, 

 though its form may be still unchanged. This applies to the case 

 now under consideration. In order to obtain the substance of 

 the mucinous membrane in a pure condition Scheibler boiled the 

 gelatinous mass (freed from adherent sugar) with milk of lime, 

 and found that only a small portion was dissolved. This fact of 

 itself bears evidence against the (chemical) uniformity of the 

 substance of the mucinous envelope of Leuconostoc. It is also 

 probable that even the dextran recovered from the lime extract 

 is a decomposition product of a more readily hydrolysed constituent 

 of the said membrane. 



The behaviour of this fission fungus towards sugars merits 

 special consideration. It has already been stated that the forma- 

 tion of mucus occurs only in such nutrient media as contain grape 

 or cane sugar, the other carbohydrates, tested on this point by 

 Liesenberg and Zopf, being found unsuitable. Leuconostoc mesen- 

 terioides produces invertin, which then splits up the cane-sugar ; 

 so it may be surmised that the development of the gelatinous 

 membrane can only occur in presence of grape-sugar (and perhaps 

 also fructose !). This does not, however, imply that lactose, maltose, 

 and dextrin are unaffected by this fission fungus ; on the contrary, 

 it ferments them and forms lactic acid, a faint evolution of gas 

 being at the same time noticeable. The presence of a small quan- 

 tity (3-5 per cent.) of calcium chloride in the nutrient medium 

 favours the production of mucus and the fermentative activity of 

 the organism, the latter being brisker when oxygen is excluded. 

 The optimum temperature for the development of this microbe 



