THE MICROBES THAT MAKE US SICK 81 
be sure which kind of mosquito is biting us, 
the only sure protection is not to give any a 
chance to bite us. 
The body has several means of fighting 
harmful microbes. One of the principal means 
of defense is found in the blood. When we 
look at a drop of blood under a microscope, 
we find that it is made up of tiny red and white 
bodies swimming in a liquid. They are called 
corpuscles. The red corpuscles, which we have 
mentioned before, give the blood its color. In 
form, they are dish-shaped. They furnish the 
food for the tissues, and are used up in the 
tissues to give the body warmth. The white 
corpuscles are irregular in shape, and it is they 
that are the chief defenders against the invad¬ 
ing microbes. Like the red corpuscles, they 
can move through the walls of the veins into 
the tissues and cavities anywhere in the body. 
As soon as the disease-microbes invade the 
body, a whole army of white corpuscles rushes 
to the spot where the microbes are and begins 
a struggle with them. Each microbe is sur- 
How does the 
body fight 
microbes? 
