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There are major differences in the metabolism of morphine and the illegal drug heroin. Morphine mostly produces its CNS effects through m-receptors, and at k- and d-receptors. Heroin has a slight affinity for opiate receptors. Most of its actions are due to metabolism to active metabolites (6-acetylmorphine, morphine, and morphine-6-glucuronide).
The modern decimal position system was the invention of the Hindus (around 800 AD), involving the placing of numerals to indicate their value (units, tens, hundreds, and so on).
There are 20 feet of blood vessels in each square inch of human skin.
Human stomach acid is strong enough to dissolve small pieces of metal such as razor blades or staples.
Earwax has antimicrobial properties that reduce the viability of bacteria and fungus in the human ear.