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bread must arise from some agency present in the flours themselves 
and independent of the chemical side of the question. Again, in 
salt-rising bread, where the sponge contains nothing but a chem- 
ically pure flour and water, an active fermentation takes place which 
must be due to the presence of organisms in the flour. Bearing 
these points in mind, the writer made a series of investigations to 
determine the micro-organisms found in the flours sold on the local mar- 
ket. A careful canvass of the market was made and samples of the flours 
sold secured, together with data concerning each. In securing these sam- 
ples every precaution was used to prevent contamination and to preserve 
similar conditions throughout. The flours examined include, first, the 
leading patent flours, most of which are Minnesota products; second, me- 
dium-grade flours; third, low-grade flours, commonly called “seconds” by 
bakers. In these tests the effort was made to determine the condition of 
each flour under as nearly similar conditions as possible. Hach experi- 
ment was repeated a sufficient number of times to secure accuracy and 
overcome abnormal conditions. The ordinary culture media were used, 
with the addition of blood serum and flour and starch paste. Plate cul- 
tures were made, using agar, wort gelatine and broth gelatine. Owing to 
the fact that many forms liquefy the broth gelatine plates, the number 
of colonies produced could not be determined, as the plate soon became a 
mass of mixed forms. Owing to the acidity of the wort gelatine, some 
forms of bacteria would not grow in it; others liquefied the gelatine, giving 
the same objection as was applied to the broth gelatine, but to a less de- 
gree. Again, moulds grew so rapidly in the wort gelatine that they 
sometimes crowded the bacteria out. Agar, on account of its nonlique- 
fying properties and comparatively unfavorable condition for the growth 
of moulds, gave the best results. In occulating for plate cultures, on an 
average of .0022 grammes of flour were used in each case, hence the 
comparative number of organisms in each flour could be determined. 
The names of the flours used are withheld for obvious reasons. 
The names of the various forms of bacteria found were not always 
obtainable, as no descriptions could be found in manuals. Of 
the twelve flours sold on the local market, seventeen distinct 
species of bacteria were found, one yeast and three moulds— 
Mucor mucedo, Aspergillus glaucus and Penicillium glaucum. These 
flours differed greatly as to the number of species obtained from 
each. Some contained but one form, while others contained as many as 
