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Parkinson's disease is both chronic and progressive. This means that it persists over a long period of time and that its symptoms grow worse over time.
Opium has influenced much of the world's most popular literature. The following authors were all opium users, of varying degrees: Lewis Carroll, Charles, Dickens, Arthur Conan Doyle, and Oscar Wilde.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
Many of the drugs used by neuroscientists are derived from toxic plants and venomous animals (such as snakes, spiders, snails, and puffer fish).
Sildenafil (Viagra®) has two actions that may be of consequence in patients with heart disease. It can lower the blood pressure, and it can interact with nitrates. It should never be used in patients who are taking nitrates.
![A tracheotomy tube in place, inserted through an opening in the front of the neck and anchored withi](https://biology-forums.com/gallery/47/medium_14755_10_09_12_7_14_27_8496830.jpeg)
![The respiratory system. (a) Sagittal section of the head and neck, revealing the organs of the upper](https://biology-forums.com/gallery/47/medium_14755_11_11_12_7_23_09_100491445.jpeg)