THE RIPENING OF CREAM. wash ae 
decreased to a comparatively few millions. This has been 
universally the case in these experiments. In one or two 
cases the cream was kept for several days longer and a bacte- 
riological examination made after it was a week old. In these 
samples the bacteria had nearly all disappeared, a few acid 
forms alone remaining, and the cream had become a nearly 
pure culture of the well-known Ozdium lactis. ‘The expla- 
nation of this disappearance of bacteria we are unable to 
give. } 
5. In all experiments the number of liquefying bacteria at 
the start was quite large, but the proportion varied from .2 to 16 
per cent. These bacteria apparently increase for a few hours, 
at least in some of the experiments; but after about 12 hours 
they decrease in proportion, and in the later periods of ripening 
become so few as to be incalculable, or disappear entirely. In 
most of the tests of completely ripened cream no traces of 
liquefying bacteria were found. 
6. The species of bacteria indicated by N. in the third 
column of the table appears to have a very peculiar relation 
to the dairies of this vicinity. It is in all cases abundant 
in the fresh cream, the smallest proportion noted being 11 
per cent. and the largest 88 per cent. In every test, however, 
the proportion of this species of bacteria decreased with the 
successive plates and became very small in the later periods of 
ripening. It did not seem to disappear absolutely, for even in 
the late periods of ripening a few colonies of bacteria N. could 
be found, but the number was so small as to be inappreciable 
in the percentages. 
7. The group of bacteria which we have here called Miscel- 
laneous, including the several species which do not produce 
acid nor liquefy gelatin, was in all cases somewhat large at the 
outset, varying from 5 to 75 per cent., but regularly decreased 
in numbers and in the late periods of ripening had entirely — 
disappeared. 
8. ‘The most characteristic feature of cream ripening con- 
sists in the growth of Z. acidilactici (206). ‘This characteristic 
lactic bacillus is found in very small numbers in fresh milk and 
cream. In other experiments, not recorded here, it has been 
found that in perfectly fresh milk the number of this species of 
S) 
