
APPLICATIONS OF BACTERIOLOGY IN EUROPE. 79 
portion of the diarrhoeal diseases among children, has led to 
the custom of sterilizing milk for the purpose of killing all 
bacteria that may be present. Sterilizing or boiling milk was 
first adopted in cases of sickness, since it was found that boiled 
milk was more advantageous to the patient than raw milk. 
Its use extended to the diet of children, and in recent years 
more and more widely among adults, until in some places the 
practice of sterilizing milk for consumption is well nigh 
universal. In Germany it is very common. In Switzerland, 
well nigh universal in cities. In England it is hardly more 
common than in the United States. The purpose of such 
treatment is manifestly two-fold. It is primarily to destroy 
all disease germs and thus render the milk harmless from the 
standpoint of infection. It is, secondly, to produce a grade 
of milk which will keep longer than without such sterilization. 
The rare use of ice in Europe makes this second advantage of 
sterilization a more important one than with us. 
As the popularity of sterilized milk has been. increasing in 
the last ten years, naturally there has developed a greater 
knowledge of methods and a perfection of machinery for ac- 
complishing the purpose. We find that the methods have 
differentiated themselves in three different directions, accord- 
ing to the amount of temperature used in bringing about the 
result. The first produces absolute sterilization, which kills 
every living bacterium that may be present in the milk. The 
second produces an almost complete sterilization, such as is 
obtained by simple boiling, while the third abandons the idea 
of killing all bacteria, and only endeavors to destroy the dis- 
ease germs and a majority of the others. In connection with 
these three methods there have been invented many machines 
of more or less value. It is not the purpose of this article to 
attempt to describe these machines, although their manu- 
facture has become a great industry in itself, and in some 
countries they have almost revolutionized the matter of milk 
distribution in cities. It is, however, necessary to refer 
briefly to the two extreme processes above mentioned, viz.: 
the complete sterilization and the process known as pasteuriza- 
tion. 
Sterilization. — The complete sterilization consists in heat- 
ing the milk to a temperature somewhat above that of boiling 
water, the actual temperature adopted varying slightly from 
about 215° (102° C.) to 221° (105° C.), or 223° (106° C.), and 
