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When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
There are more bacteria in your mouth than there are people in the world.
Serum cholesterol testing in adults is recommended every 1 to 5 years. People with diabetes and a family history of high cholesterol should be tested even more frequently.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
Although the Roman numeral for the number 4 has always been taught to have been "IV," according to historians, the ancient Romans probably used "IIII" most of the time. This is partially backed up by the fact that early grandfather clocks displayed IIII for the number 4 instead of IV. Early clockmakers apparently thought that the IIII balanced out the VIII (used for the number 8) on the clock face and that it just looked better.