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Vampire bats have a natural anticoagulant in their saliva that permits continuous bleeding after they painlessly open a wound with their incisors. This capillary blood does not cause any significant blood loss to their victims.
Intradermal injections are somewhat difficult to correctly administer because the skin layers are so thin that it is easy to accidentally punch through to the deeper subcutaneous layer.
The most destructive flu epidemic of all times in recorded history occurred in 1918, with approximately 20 million deaths worldwide.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
Fewer than 10% of babies are born on their exact due dates, 50% are born within 1 week of the due date, and 90% are born within 2 weeks of the date.