The investigators could distinguish human hair from animal hair by the patter of pigmentation and by the medullary index.
The pigmentation in human hairs is denser toward the cuticle, whereas in animal hair is denser toward the medulla. Human hairs are usually one colour throughout the whole length, while animal hairs may change colour suddenly.
The medulla in humans is thinner than in animals: the medullary index for human hairs is 0.33 or less; the medullary index for animal hairs is 0.5 or more.
The outer membrane is technically the skin and covers the organelle.
The inner membrane folds over many times and creates layered structures called cristae.
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