
MILK PRESERVED AT SEVENTY AND FIFTY DEGREES. 51 
bacteria which are present at the time of curdling is subject to 
the widest variations, being in some cases as low as 282,000,000 
and in other cases as high as 1,659,000,000; in one case more 
than five times as great as in the other. She amount of acidity 
which was present at the time of curdling is not given in the 
tables. It was also somewhat variable, ranging from .68 to 
.87 per cent., and was about the same in samples where the 
number of bacteria was very large as where it was compara- 
tively low. From these figures, however, no conclusions of 
importance can be drawn. 
From this series of experiments the most important con- 
clusions are: 1. ‘That straining through cheese cloth, while 
it removes a considerable quantity of the dirt, has practically. 
no effect upon the keeping property of the milk. 2. A de- 
crease of twenty degrees, from 70° to 50°, makes a most ex- 
traordinary difference, (a) in the rapidity of bacteria growth, 
(b) in the species of the bacteria that grow in the milk, 
-and (c) in the keeping property of the milk, increasing the 
latter most surprisingly. Milk kept at 70° in these experi- 
ments was sour enough to curdle in about two days and a 
half, while milk which was kept at 50° remained in some cases 
20 days or more before it was sufficiently acid to curdle. In 
connection with the last point it should be stated, however, 
that although this milk kept without curdling for 20 or more 
days, this cannot be interpreted as meaning that the milk was 
fit to use for this length of time. A bacteriological examina- 
tion of such milk, which was made, showed that the number of 
bacteria present in these old non-curdled samples was extremely 
great, far greater than any number given in the tables. But | 
for some reason, which we have not yet explained, the develop- 
ment of the acid organisms had not taken place in such a way 
as to cause the curdling of the milk. 
