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When Gabriel Fahrenheit invented the first mercury thermometer, he called "zero degrees" the lowest temperature he was able to attain with a mixture of ice and salt. For the upper point of his scale, he used 96°, which he measured as normal human body temperature (we know it to be 98.6° today because of more accurate thermometers).
Throughout history, plants containing cardiac steroids have been used as heart drugs and as poisons (e.g., in arrows used in combat), emetics, and diuretics.
Pubic lice (crabs) are usually spread through sexual contact. You cannot catch them by using a public toilet.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.