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More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
In most cases, kidneys can recover from almost complete loss of function, such as in acute kidney (renal) failure.
Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.
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.
It is believed that humans initially contracted crabs from gorillas about 3 million years ago from either sleeping in gorilla nests or eating the apes.