THE GERMICIDAL PROPERTY OF MILK. 
By Milton J. Rosenau, 
Director Hygienic Laboratory , Public Health and Marine- Hospital Service , and 
George W. McCoy, 
Passed Assistant Surgeon , Public Health and Marine- Hospital Service. 
INTRODUCTION. 
Judged by the number of colonies that develop upon agar plates, 
the bacteria in milk first diminish then increase in number. This 
occurs only in raw milk during the first few hours after it is drawn. 
Although the bacteria seemingly decrease in number they never disap- 
pear entirely. After this initial decrease there is a continuous and 
great increase until the milk contains enormous numbers. 
It was early noted that under certain conditions raw milk may keep 
longer than heated milk. In other words, the property of milk to 
restrain the growth of bacteria is destroyed by heat. 
Before this so-called germicidal property of milk was discovered it 
had been observed that fresh blood, or blood serum, had distinct 
powers of destroying bacteria. Further, that blood resists putrefac- 
tive and fermentative changes. It is now clear that blood, apart 
from the phagocytic action of its cells, has definite germicidal proper- 
ties. This is due to substances di^olved in the blood serum which 
have the power of clumping, killing, or dissolving the bacterial cells. 
The germicidal properties of blood are destroyed by heat and disap- 
pear spontaneously in a short time after the blood has been removed 
from the body. 
This power of the blood is an important protection against bac- 
terial invasion. Similar uses have been assigned to the “ antibodies” 
in milk. 
Not only the blood, but other body fluids have germicidal proper- 
ties in varying degree, so that it was not surprising when similar 
! powers were attributed to milk, especially when we consider that 
the fluid part of milk, with many of its dissolved constituents, is 
- secreted directly from the blood. 
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24907— Bull. 41—08 29 
