as 
PH 3 
QUALITATIVE ANALYSIS OF MARKET MILK. SOs 
showed no such result, we regard this as one of the incidental 
_ irregularities which-are inevitably due to the bunching of bac- 
teria together and the failure to distribute them uniformly. 
Beyond these differences a comparison of the analyses given 
shows that the results of the three media are not very different, 
and that the analyses agree moderately well. 
The table shows clearly that it is impossible to distribute the 
_ bacteria through the milk in such a way that a cubic centimeter 
will give an average sample. For example, in column three 
the percentage of liquefiers is 23.1, while in column four it is 
12.6, and in column two it is only 6.8. Now the liquefiers are 
always very easily distinguished and can never be confounded 
with other colonies. This difference must therefore indicate a 
difference in numbers and not a failure to properly differentiate 
the species. Such irregularities are to be expected. A micro- 
scopic study of a drop of milk shows that the bacteria have a 
tendency to cling together in masses, little bunches of the same 
species being found floating in the milk. In our analysis we 
endeavor to break these up as much as possible by thorough 
shaking, but we cannot expect to do this in all cases, and stich 
little groups will occasionally produce such irregularities as 
those just pointed out. In other words, to get a strictly aver- 
age sample of a lot of milk seems to be impossible, and at best 
the results of a differential analysis of milk will show occasional 
irregularities due to the grouping of bacteria. This fact, of 
course, detracts from the value of any single analysis, and 
greatly increases the amount of work necessary, since it is pos- 
sible to rely only upon results that represent the average of 
many samples. The irregularities of the figures in Table 14 
are much higher than usual, as will be seen from the two tables 
which follow. 
Experiments of which Table 14 is a sample seemed to indi- 
cate that while peptone gelatin gives the larger bacteria count, — 
either of the milk culture media gives a sharper differentiation. 
This does not show so well from the figures given in the table 
above as from a study of the plates, the difference being in the 
sharpness of the distinction of the colonies. In the milk cul- 
ture the lactic bacteria produced rapidly a clear, sharp, very 
red colony, easily distinguishable from others, whereas in, the 
peptone gelatin the same species produced a much less noticeable 
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