
QUALITATIVE ANALYSIS OF MARKET MILK. 79 
But, making due allowance for this possibility of. error, it is 
manifest to us that the presence of sinall numbers of bacteria 
indicates, as a rule, the presence of a large number of varieties. 
4. ‘The liquefying bacteria in general vary inversely with 
the total numbers. The liquefying bacteria, many of which 
produce putrefactive decomposition, are a group of organisms 
very undesirable in milk. They tend to produce the putrefac- 
tion of milk, and when they are present in large numbers must 
render the milk unwholesome. From the preceding table, the 
relation of the percentages of liquefiers to the total numbers of 
bacteria is indicated. It will be seen that, although there are 
some irregularities, nevertheless the tendency is exactly the 
reverse of that of the lactic organisms. The percentage of 
the liquefiers is commonly largest in the samples of milk con- 
taining the smallest number of bacteria, and smallest in the 
samples of milk containing the largest number of bacteria. In 
the older samples, where the lactic organisms had become quite 
abundant, the liquefying forms sometimes almost disappeared, 
and always became relatively very few in numbers. ‘This fact 
was shown better in the previous paper, where still older sam- 
ples of milk were analyzed. In the fresh milk, where the num- 
ber of bacteria was small, the percentage of liquefiers shows 
the widest variation, as would be expected from the different 
conditions of contamination; but if liquefiers are present in fresh 
milk, the percentage is likely tobe high. In general, then, the 
percentage of liquefiers is the reverse of the percentage of lactic 
organisms. In samples of fresh milk they are likely to be 
abundant, while in the samples of older milk this grolip of 
organisms has a Ee though not universal, tendency to 
disappear. 
5. The liquefying bacteria vary with the seasons of the year. 
The experiments described ran through a series of months be- 
ginning with February and extending until about the first of 
July. ‘They extended through the period of winter feeding into 
the period of spring feeding, and up to the time when there 
appears in the milk and in the butter the so-called June-grass 
flavor. From the table it will be found that there is a general 
" increase in numbers of bacteria in the spring months, the num- 
bers found in May and June being, on the whole, considerably 
