ALKALI-FORMING BACTERIA FOUND IN MILK. 33 
Nessler's reagent; consequently all the cultures in sodium-nitrite- 
lactate medium were tested for the presence of ammonia. The test, 
however, was found to be negative and since it was known that these 
bacteria could utilize ammonia as a source of nitrogen the results 
indicate that as the nitrite was reduced to ammonia the latter 
was immediately used up. 
The results showing the reduction of nitrate and nitrite by the 
alkali-forming group of bacteria are of particular interest, since they 
point out the difficulty of obtaining accurate tests for these reductions 
without a thorough understanding of the physiology of the bacteria. 
ARBITRARY GROUPING OF THE ALKALI-FORMING BACTERIA FROM MILK. 
An attempt has been made to arrange into groups the 68 alkali- 
forming bacteria used in this study in order to show the possibility 
and emphasize the use of the organic-acid salts, carbohydrates, and 
alcohols as test substances when used as the only source of carbon 
in a synthetic medium. In the chart, figure 2, it may be seen 
that the cultures have been divided first according to their morphology 
into cocci and bacilli, then further subdivided on the basis of their 
fermentation of dextrose. After the division of the cultures into 
positive and negative dextrose, they are again divided into sub- 
groups according to their ability to ferment mucic, tartaric, malonic, 
or glyceric acid salt. In this grouping, in order to differentiate fur- 
ther and bring out the main points of difference in the cultures, the 
following organic salts were used — formic, butyric, valeric, hippuric, 
uric, and urea. While these organic-acid salts were used to group 
the cultures, it often happened that other easily fermented organic- 
acid salts not mentioned had to be utilized to distinguish the different 
subgroup members further. Examples of such are the salts of 
malic, acetic, and citric acids. 
For the convenience of those who may study alkali-forming organ- 
isms each subgroup has been given an arbitrary number. The fer- 
mentation of dextrose and the salts of the organic-acid salts men- 
tioned were, for the purpose of this paper, considered primary char- 
acteristics in distinction to the secondary characteristics which are 
shown in the lower half of figure 2. It is of interest to observe that 
the alkali-forming bacteria studied in this work and grouped accord- 
ing to what are considered primary characteristics, also had secondary 
characteristics which correlated with the primary. Thus by refer- 
ring to the chart it may be seen that all the fluorescent cultures fell 
into subgroup 4, all the gelatine liquefiers fell into subgroup 6, while 
all the cultures that fermented the alcohols, such as mannite and 
glycerin, fell into subgroup 9. The only cultures that showed gas 
in dextrose broth also were in subgroup 9. The pigment formers, 
which were also the cultures that fermented saccharose, fell into 
