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Blood analysis. Hand loading blood samples into a Vitros Analyser for automatic blood analysis. The sample tubes are bar coded for identification. This machine can be used to assess liver function, as well as to measure the levels of urea, electrolytes and serum lipids. The liver regulates the levels of many substances in the blood and so abnormal levels of blood chemicals such as bilirubin, the breakdown product of red blood cells' pigment, may be due to a liver disorder. The lipid concentration of the blood's serum, part of the fluid blood plasma, rises after a fatty meal. High levels of urea, which is a product of protein breakdown, may indicate kidney failure. (KEYSTONE/SCIENCE PHOTO LIBRARY/JIM VARNEY)