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In 1886, William Bates reported on the discovery of a substance produced by the adrenal gland that turned out to be epinephrine (adrenaline). In 1904, this drug was first artificially synthesized by Friedrich Stolz.
Over time, chronic hepatitis B virus and hepatitis C virus infections can progress to advanced liver disease, liver failure, and hepatocellular carcinoma. Unlike other forms, more than 80% of hepatitis C infections become chronic and lead to liver disease. When combined with hepatitis B, hepatitis C now accounts for 75% percent of all cases of liver disease around the world. Liver failure caused by hepatitis C is now leading cause of liver transplants in the United States.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
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.
Earwax has antimicrobial properties that reduce the viability of bacteria and fungus in the human ear.
![(a) Feeding by bear on salmon results in large allochthonous inputs of nutrients into (b) the forest](https://biology-forums.com/gallery/47/medium_33_17_02_12_7_02_16_2035460.jpeg)
![The conduction system of the heart; traces the path of the electrical impulse that stimulates the he](https://biology-forums.com/gallery/47/medium_14755_10_09_12_7_22_09_85202259.jpeg)