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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.
There are 60,000 miles of blood vessels in every adult human.
Once thought to have neurofibromatosis, Joseph Merrick (also known as "the elephant man") is now, in retrospect, thought by clinical experts to have had Proteus syndrome. This endocrine disease causes continued and abnormal growth of the bones, muscles, skin, and so on and can become completely debilitating with severe deformities occurring anywhere on the body.
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.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.