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Robert Hermann Koch (11 December 1843 – 27 May 1910) was a German physician who developed Koch's postulates. [1]Koch's postulates (/ k ɒ x / KOKH) [2] are four criteria designed to establish a causal relationship between a microbe and a disease.
Human blood in veins is not actually blue. Blood is red due to the presence of hemoglobin; deoxygenated blood (in veins) has a deep red color, and oxygenated blood (in arteries) has a light cherry-red color. Veins below the skin can appear blue or green due to subsurface scattering of light through the skin, and aspects of human color ...