154 BACTERIA IN MILK. 
way, it becomes viscid, and finally it may be so slimy that it can 
be drawn out into long threads. At the same time it has a sweetish 
taste. Such milk is practically worthless. It cannot be used for 
butter-making, for the cream will not separate. It will not be used, 
for drinking 01 cooking purposes, although there seems to be no 
reason for believing that it is not perfectly wholesome. In some 
countries, indeed, such slimy milk is a favorite beverage; but in this 
country most people, not wishing to drink slime, will 
$#* throw it away. Sometimes such an infection proves 
'Vi very troublesome. It may spread through a whole 
i! farming district, affecting many dairies and continuing 
\f for a long time. Although not always easy to follow, 
ft* such infections may generally be traced to some com- 
FiG.36. B. mon source of distribution. For example, a central 
the " common creamery, receiving such slimy milk from some patron, 
cause of slimy mav distribute the trouble over the whole patronizing 
district by returning to the farmers the milk vessels 
not properly sterilized. 
The cause of this sliminess is the growth of bacteria. Several 
different kinds of bacteria have been discovered with this property. 
The best known of them, and probably the most common, is one that 
has been named B. lactis mscosus (Fig. 36). This has been found 
to be the cause of the trouble in Europe, and a similar if not the 
identical organism has been found in America. It appears to be 
a very vigorous organism, and, when once present, will grow so 
rapidly as to make the milk slimy in spite of the action of the ordinary 
acid-forming bacteria that may be present. 
To understand the sources from which this troublesome organism 
is derived may be a matter of great importance to a dairyman. 
Three sources have thus far been detected: i. Sometimes it may 
come from water used in washing the milk cans or, more likely, 
from the water in which the cans have been standing to cool the 
milk. 2. It may come from the udder of the cow; perhaps a single 
cow in a herd being thus infected and her milk contaminating that 
of the whole dairy. 3. Slimy milk bacteria have been found in the 
dust of the air in dairies. If, therefore, a dairy is troubled with 
