Abstract
At least some of the skin and hair pigments of mammals (melanins) appear to be produced from the precursor, tyrosine, and it has recently become possible to demonstrate tyrosinase activity in normal mammalian skin. A histochemical demonstration of melanin formation from tyrosine was made in the case of non-pigmented human skin subjected to erythema doses of ultra-vimolet irradiation (1), and tyrosinase activity has also been demonstrated in skin homogenates from mice and foetal guinea pigs by means of manometric measuremeats of oxygen consumption (2-4). Since this pigment-forming process has been demonstrated either histochemically or manometrically, it was considered desirable to attempt to demonstrate both aspects of the process in the same sample of tissue.
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