QUALITATIVE ANALYSIS OF MARKKET MILK. ro Or 
the suggestion was made that it is the organisms which pro- 
duce albuminoid decomposition which are responsible for at 
least some of these flavors in milk products. It is therefore to 
us a suggestive fact to find that when the cows are fed upon 
grass there begins an increase in these particular types of bac- 
teria, and that the milk develops the so-called grass flavor. 
The general conclusion seems to be warranted that this in- 
crease in the percentage of liquefiers is one of the factors which 
account for the development of the grass flavors that appear in 
the early summer months. 
6. ‘The different samples of milk showed the widest differ- 
ences in the number of varieties that were present. In some 
cases the number of kinds of bacteria was only four or five, 
these samples being the ones where the percentage of lactic 
organisms was high. In other cases, however, the varieties 
were very great. In the sample No. 27, a test made in May, 
although the number of bacteria was about 50,000, there were 
no less than 17 easily recognized species of bacteria distin- 
guished on our plates, and these 17 would have been increased 
somewhat if it had been possible to differentiate completely 
all of the species. Between these two extremes the different 
samples showed great variations in the number of kinds of bac- 
teria present. 
MODIFICATIONS OF METHODS OF STUDY. 
Our work up to this point was done with the culture media 
described in our previous report. By the time this series of 
‘experiments was finished certain imperfections in the culture 
media were recognized, and there appeared several points at 
which the method possibly might be improved. The chief 
points where improvement seemed to be needed were two. 
1. Sterilization of the gelatin culture media always decolorized 
litmus which it contained, and although the solution after sub- 
sequent standing again acquired a blue color, the results were 
somewhat irregular. Moreover, it was not possible to obtain 
the same depths of blue color in different lots of gelatin. 
2. Certain facts led us to suspect that the culture media made 
of peptone, etc., did not furnish the best condition for the 
growth and differentiation of milk bacteria. It would seem 
