59G VITAL ACTIONS OF THE LOWER FUNGI. 



Lactic Fermentation. 



fermentation ^^ e mater ^ a ^ s necessary are grape-sugar, cane-sugar, 

 milk-sugar, marmite, sorbite, inosite. Cane-sugar and 

 milk-sugar are probably in the first place converted into 

 glucose. Spontaneous fermentation is most frequently 

 observed in milk ; it probably also plays a part in the 

 preparation of bread and leaven, and frequently occurs 

 in the fabrication of starch, and in the saccharine juice 

 of beet-root. We can artificially obtain a lactic fer- 

 mentation either by leaving milk to stand at about 

 30 C. for three or four days, or by mixing a weak sugar 

 solution with somewhat old cheese and with purified 

 chalk, and keeping the mixture for several days at 

 30 to 35 C. ; in the latter case the lactate of lime 

 which is formed can be easily obtained (see Schiitzen- 

 berger, page 172). 



Fermentative The bacillus acidi lactici is in most cases the exciting 

 agent of the fermentation. But the lactic fermentation 

 is by no means confined to this one species of bacterium, 

 but, on the contrary, a large number of cocci and bacilli 

 which have been mentioned above, share with it the 

 fermentative power, and are only distinguished from it 

 by the fact that the quantitative result of their action is 

 much less, and that they are by no means so widely dis- 

 tributed as the ordinary lactic acid bacillus. Hence in 

 all spontaneous fermentations we find that the lactic 

 bacilli usually take part, and generally in much the 

 largest numbers. 



Nature of the The nature of the chemical decomposition has not yet 



tion mp been completely explained. Formerly the attempt was 



made to explain the decomposition of sugar in the lactic 

 fermentation by the simple formula, CJI^0 6 (glucose) = 

 2 (C 2 H 4 , OH, COOH) (lactic acid), and Miller also 

 states that he has observed in the case of some bacteria 

 this simple decomposition of the molecules of sugar. 

 Such a process, without any development of gas, and 

 without any more marked alteration in the molecule, 

 could not be regarded as fermentation according to the 



