CLASSIFICATION OF DAIRY BACTERIA. a 
fragmentation and its sour odor, is never developed unless some 
of the organisms included in my No. 208 species are present. 
Ordinary sour milk, according to my observations, is produced 
by these three organisms, and probably in the spontaneous 
souring of milk all three are present. 
I am convinced that here also the various bacteria which 
I have included under No. 208 do not represent a single 
bacterium, but rather a group of allied varieties, and as a 
group represent a most important dairy organism. In looking 
through the literature upon dairy bacteria, it appears to me 
that many of the lactic organisms that have been described by 
different observers belong to this group. The original 2. actdz 
factict of Hueppe apparently belonged here. Here, too, prob- 
ably must be placed Bacterium lactis actdi, Marpmann, Bacillus 
lactis acidi, Marpmann, Bacillus acid? lactict, J. and II., of Gro- 
tenfelt, Vo. 8 of Eckles, and doubtless several others. In the 
pure cultures used for cream ripening in European countries, 
known as the culture of Lorenz, the organisms appear to belong 
to this same type. The two forms recently isolated from Edam 
cheese by Leichmann and Bazarewski and called Bacterium caest, 
I. and II., also belong to this series. It is quite unlikely that 
these different organisms are the same, although their morpho- 
logical and cultural characters in general accord. All of these 
facts indicate that in the species which I have at present called 
Bacillus lactis aerogenes there are grouped together a number otf 
types with great similarity, but with at least different physi- 
' ological characters. 
The third type of bacteria which I have found so abundant 
as to call it a distinctive dairy bacterium of this region is 
my MW. lactis varians, No. 113. ‘This has been sufficiently 
described elsewhere, and as already mentioned is a very highly 
variable Micrococcus both as to chromogenic powers and power 
of liquefying gelatin. This species is common in fresh milk 
and probably exists in the milk ducts. It is commonly over- 
grown by the lactic organisms and is Jess common in old milk. 
It is by no means universally found and may be only a local 
species. 
Several other species in my list are quite common in milk, 
but I think that these four must be regarded as the chief dairy 
bacteria of this region. 
