MECHANISM OF MOVEMENT OF EPIDERMIS, ESPECIALLY ITS MELANOPHORES, IN WOUND HEALING, AND BEHAVIOR OF SKIN GRAFTS IN FROG TADPOLES

Abstract

In Rana clami-tans tadpoles 70-80 mm. long autotransplants of white ventral skin grafted to the pigmented backs retained their specificity. Lateral and dorsal autotransplants in which the patches of skin were rotated through 90[degree] and 180[degree] also retained their specificity. Homoiotransplants of white ventral skin transferred to the pigmented backs of tadpoles did not persist unchanged. These grafts were replaced by host tissue which carried pigment cells. Soon after transplantation, both auto- and homoiotransplants became reddened as a result of enlargement of the dermal blood vessels of the graft. There is considerable evidence that the enlargement of the blood vessels is due to pressure which, in the absence of normal tonus, mechanically stretches the vessels, the nerves having been cut at the time of transplantation. Radial arrangement of the epidermal melanophores occurs around homoiotransplants and skin wounds, i.e., wherever there is translatory movement of the epidermis. In any migrating epidermis in which the melanophores are expanded, their long axes tend to become parallel to the direction of migration. The position of the individual melanophores, in radial or parallel alignment, is a consequence of movement of the epidermal cells near a wound and not due to independent orientation of the melanophores. The epidermal cells nearest the wound move first and most rapidly, thereby tending to rotate the elongated melanophores into the line of movement of the epidermis. Since the movement of the epidermis is centripetal, the melanophores become arranged radially around the point toward which the epidermis moves.