355 
\ 
were found to aid lactic acid fermentation, but leucine and glycocoll 
were found to have no effect upon the process. 
The general trend of more recent investigations on the subject of 
lactic acid fermentation has been to show that the change of milk 
sugar into lactic acid takes place under the influence, either direct or 
indirect , of a whole series of micro-organisms, whose number has been 
considerably augmented by recent investigations in this field. Marp- 
mann (6), for example, during the summer of 1885 investigated the 
micro-organisms of cow’s milk in the neighborhood of Goettingen and 
detected five seemingly new and different species of organisms, 
which more or less strongly induce the lactic acid fermentation in 
solutions of cane sugar and also in milk. 
Leaving out of consideration the levure lactique of Pasteur, the first 
of these organisms whose morphological and biological character- 
istics seems to have been determined with sufficient accuracy is the 
Bacillus acidi lactici of Hueppe (7) . It is now known that in addition 
to the Bacillus acidi lactici (Hueppe) the following organisms can bring 
about the lactic acid fermentations, viz, Bacillus aerogenes, Bacillus 
coli, Bacillus lactis acidi (Leichmann and others), Streptococcus 
lacticus (Kruse), Streptococcus pyogenes, Pneumonococcus A and 
Pneumonococcus B, Bacillus Delbruecki (Leichmann), Bacillus 
acidificans longissimus (Lafar), etc. 
Beyerinck (8) has also made exhaustive studies of the lactic- acid 
ferments employed in the arts. This author applies the name 
Lactobacillus Delbruecki to all species of the lactic- acid ferment 
which can be isolated by the gelatin-must method. These organ- 
isms, according to this author, however, are not the active agents of 
a good industrial ferment. On the other hand from such a ferment 
he was able to isolate the Lacto bacillus fermentans. This organism 
when cultivated under good conditions yields only lactic acid and no 
volatile acids. The minimum temperature of its activity he found 
to be 25° C., the optimum temperature 41°-42° C., and the maximum 
temperature 50° C. These observations furnish an interesting con- 
firmation of the earlier work of Richet so far as the influence of 
temperature on the lactic fermentation is concerned. According 
to Beyerinck the lactic organisms studied by him can be mutually 
transformed into one another by cultivation. 
Heinemann (9) has called attention to the similarity existing 
between Bacillus acidi lactici (Hiippe and others) and Bacillus (lactis) 
aerogenes (Escherich) and also to the similarity of Bacillus lactis 
acidi (Leichmann and others), Streptococcus lacticus (Kruse) and 
Streptococcus pyogenes, and in a more recent communication (10) 
on the kinds of lactic acid produced by lactic acid bacteria, to the 
similarity of Streptococcus lacticus with Streptococcus pyogenes and 
