Cells of the substantia nigra of a human brain. The heavy deposits of melanin in the cytoplasm of these cells make a very striking picture. The significance of this pigment is quite unknown. It develops a few years after birth, and reaches its maximum intensity at puberty. The substantia nigra is one of the elements of the extra-pyramidal system, receiving fibres from the globus pallidus. The photograph is at a magnification of X 158.

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