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What are the three ways that forensic scientists can distinguish human hair from animal hair? Describe each way.
Human hair can differ from animal hair by pattern of pigmentation, medullary index, and cuticle type. In humans, the pigmentation tends to be denser towards the cuticle, while in animals the pigmentation is denser towards the medulla. Animal pigments are found in solid masses (ovoid bodies), especially in dogs and cattle, and can change color abruptly in a banded pattern. Human hair is usually one color along the length. If the ratio of the medulla’s diameter to the hair’s diameter, or medullary index is 0.5 or greater the hair is an animal’s. If the medullary index is 0.33 or less, the hair is a human’s. Human hair has imbricate, or flattened and narrow, scales on the cuticle, while animals can have many different types, including coronal, or appearing like a stack of crowns and spinous, or resembling petals.