170.WHAT DO WHITE BLOOD CELLS DO?
You can see that blood, so necessary for life, is not a simple thing. Many different substances have their special work and importance.
Although the red cells are by far more numerous in the blood and give blood its color, the white blood cells have a critical role, too. The white blood cells are called leukocytes.
169.IS THERE ANY GROUP OF PEOPLE WHO ARE GIANTS?
We all know that there are Pygmies. But is there any group of people taller than the average, as the Pygmies are shorter?
The answer is no. Height varies throughout the world. Some peoples, such as the Eskimos, Lapps, and certain Indian Tribes in South America are short. Some of the native tribes of eastern Africa have an average height of 1.8 meters or more. But they are not giants.
168.HOW DOES THE BODY MAKE BLOOD CELLS?
In the body of an adult human being, there are about six litres of blood. Floating about in this liquid there are approximately 25 billion blood cells!
It is almost impossible for us to imagine such a tremendous quantity, but this might give you an idea. Each blood cell is so tiny that it can only be seen under a microscope. If you could make a string of these microscopic cells, that string would go four times around the earth!
