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Hippocrates noted that blood separates into four differently colored liquids when removed from the body and examined: a pure red liquid mixed with white liquid material with a yellow-colored froth at the top and a black substance that settles underneath; he named these the four humors (for blood, phlegm, yellow bile, and black bile).
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.
In 2006, a generic antinausea drug named ondansetron was approved. It is used to stop nausea and vomiting associated with surgery, chemotherapy, and radiation therapy.
More than 34,000 trademarked medication names and more than 10,000 generic medication names are in use in the United States.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
![The nitrogen cycle. Numbers represent fluxes as 1012 g N per year (data from Schlesinger 1991, after](https://biology-forums.com/gallery/47/medium_33_17_02_12_7_02_17_2038129.jpeg)
![History of the number of observed sunspots during the last 250 years, which shows the ~11-year solar](https://biology-forums.com/gallery/47/medium_12359_16_06_12_7_11_02.png)