This is because the white cells of our blood fight the germs and kill them (p. 53).
In most pricks and cuts the white cells of the blood can kill all these enemies and also heal the cut.
The offices that the blood performs in the body are believed to be due mainly to the action of the white cells.
Unfortunately, the illustration of blood here reproduced does not show the white cells.
It is the preponderance of these white cells which imparts the peculiar milky color to pus.