
72 STORRS AGRICULTURAL EXPERIMENT STATION. 
from milk. Bacteria are so small that no method of filtering 
has been, or probably can be, devised which can remove them 
and not also remove the fat particles from the milk. Such a 
filtering only removes the larger particles of dirt, but this is 
itself useful. In other cases the cleaning is produced by 
centrifugal force, the milk being passed through a special 
machine, which is something of the same nature as the sepa- 
rator, but in which the revolutions are less rapid and not suff- 
cient to separate the cream from the milk, but are sufficient to 
separate all of the heavier particles of filth. Such a cleaning 
by filtration or by centrifugal force is of decided value to the 
purity of the milk, and the better milk companies in European 
cities are adopting the one or the other of these two methods. 
An incidental result has been in the adoption of cement 
floors in most of the better establishments that have to do with 
the distribution of milk. The old style of wooden floors has 
been found to become so thoroughly impregnated with 
bacteria and so impossible to clean that they have been quite 
generally abandoned. Indeed, in some cities there is a police 
regulation that milk shall not be allowed to stand for any 
length of time in rooms with wooden floors. As a result, the 
use of cement flooring is rapidly extending and has been 
almost universally adopted. This change may be beyond 
question traced largely to the knowledge of bacteriology. 
It has of course long been known that in order to keep milk 
it must be kept cold. Nevertheless, some of the facts discovered 
"in this connection in recent years have been of practical value. 
It has been learned that the bacteria grow most readily, as a 
rule, at temperatures near that of the body of the cow and, 
therefore, when the milk is drawn from the cow it is at a tem- 
perature at which the bacteria grow most vigorously. As a 
result of this fact there has been introduced, almost universally, 
the method of cooling the milk to as low a temperature as pos- 
sible immediately after it is drawn from the cow. For accom- 
plishing this, a considerable variety of forms of apparatus 
have been invented in the form of milk coolers which use 
either cold water or ice, and through which the milk is allowed 
to pass at once after being drawn from the cow. The advan- 
tage of this cooling is very great indeed, and it has made possi- 
ble the extension of the milk industry in places and under 
circumstances that would have been impossible otherwise. In 
European dairies this matter is of even more importance than 
in American dairying. One of the most striking differences 
