|
|
When blood is deoxygenated and flowing back to the heart through the veins, it is dark reddish-blue in color. Blood in the arteries that is oxygenated and flowing out to the body is bright red. Whereas arterial blood comes out in spurts, venous blood flows.
Adult head lice are gray, about ? inch long, and often have a tiny dot on their backs. A female can lay between 50 and 150 eggs within the several weeks that she is alive. They feed on human blood.
The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."
Since 1988, the CDC has reported a 99% reduction in bacterial meningitis caused by Haemophilus influenzae, due to the introduction of the vaccine against it.
Elderly adults are living longer, and causes of death are shifting. At the same time, autopsy rates are at or near their lowest in history.