670 BACTERIA IN ARTICLES OF FOOD. 
the bacteria which produce unwholesome chauges in milk are several 
which cause it to become viscous or soapy. Among these we may 
mention Micrococcus lactis viscosus of Conn, Micrococcus Freuden- 
reichi of Guillebeau, Bacillus mesentericus vulgatus, and Bacillus 
lactis saponacei of Weighmann and Zirn. A considerable number 
of bacilli are known which give rise to the production of butyric 
acid fermentation in milk and its products. Some of these are an- 
aérobic and some aérobic. The list includes the following: Bacillus 
butyricus of Prazmowski, Bacillus of Liborius, Bacillus of Botkin, 
Bacilli of Kadrowski. 
The bitter taste which milk and cheese sometimes acquire is due 
to the presence of special bacterial ferments; among these the best 
known are an aérobic, liquefying micrococcus described by Conn, a 
bacillus described by Weighmann, Micrococcus casei amari and Ba- 
cillus liquefaciens lactis amari of De Freudenreich (1895). 
In fresh butter of good quality comparatively few microérganisms 
are found, but the researches of Conn show that the characteristic 
and agreeable flavor of fresh butter is due to, or at least may be imi- 
tated by, a bacillus which is concerned in the ripening of cream 
under normal conditions. Cultures of this bacillus (Bacillus 41 of 
Conn) have already been used in a practical way by butter makers 
to improve the flavor of their product. 
Kreuger (1890) obtained from “cheesy butter,” having a disa- 
greeable odor, various bacteria. Among these the most numer- 
ous were an oval micrococcus (Micrococcus acidi lactici, Kreuger), a 
slender bacillus resembling Bacillus fluorescens, and Bacillus acidi 
lactici of Hueppe. 
Klecki (1894) has isolated from rancid butter several bacteria not 
previously described, one or more of which are no doubt concerned , 
in the production of the rancid taste and odor. These are described 
under the following names: Bacillus butyri, Diplococcus butyri, a 
bacillus resembling Iodococcus vaginatus of Miller, Tetracoccus 
butyri, Bacillus butyri No. 2. 
Duclaux (1887) has isolated from different kinds of cheese no less 
than eleven different species of bacteria, which he believes are con- 
cerned in the “ripening process.” Seven of these are aérobie and 
four anaérobic species. Adametz (1889) has also isolated and studied 
a number of species to which he attributes the ripening of cheese. 
More recently Henrici (1895) has studied the bacterial flora of 
cheese, and Marchal (1895) has shown that the ripening of certain 
kinds of cheese (fromages mous) is probably due to Oidium lactis. 
Meats, even when salted and smoked, may contain living patho- 
genic bacteria which were present prior to the death of the animal, 
and, when not properly preserved, are of course liable to be invaded 
by putrefactive bacteria. 
