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It is believed that the Incas used anesthesia. Evidence supports the theory that shamans chewed cocoa leaves and drilled holes into the heads of patients (letting evil spirits escape), spitting into the wounds they made. The mixture of cocaine, saliva, and resin numbed the site enough to allow hours of drilling.
During the twentieth century, a variant of the metric system was used in Russia and France in which the base unit of mass was the tonne. Instead of kilograms, this system used millitonnes (mt).
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.
People often find it difficult to accept the idea that bacteria can be beneficial and improve health. Lactic acid bacteria are good, and when eaten, these bacteria improve health and increase longevity. These bacteria included in foods such as yogurt.
Blood is approximately twice as thick as water because of the cells and other components found in it.