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1. A derived protein obtained by the hydrolysis of collagen in the connective tissues of the skin, bones, and joints of animals. It is used as a food, in the preparation of pharmaceuticals, and as a medium for culture of bacteria. It is unusual as an animal protein in that it is not a good source of essential amino acids.
2. The substance on an x-ray film in which the silver halide crystals are suspended in the radiographic emulsion.

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