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Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
Vaccines cause herd immunity. If the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get the disease since others are less likely to become sick from it and spread the disease.
During pregnancy, a woman is more likely to experience bleeding gums and nosebleeds caused by hormonal changes that increase blood flow to the mouth and nose.
The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.
If all the neurons in the human body were lined up, they would stretch more than 600 miles.

