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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.
Nitroglycerin is used to alleviate various heart-related conditions, and it is also the chief component of dynamite (but mixed in a solid clay base to stabilize it).
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
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.
About 3% of all pregnant women will give birth to twins, which is an increase in rate of nearly 60% since the early 1980s.