Prospects of regeneration in man.

Reports of fingertip regrowth in children are interpreted in the perspective of epimorphic regeneration in lower forms and in relation to a few other examples in mammals. The latter include cases of antler replacement in deer as well as ingrowth from the margins of holes cut in bat wing membranes and in the external ears of rabbits, pikas, cats, and echolocating bats. It is suggested that the relative inadequacy of regeneration in warm-blooded vertebrates may be attributed to the precocity with which they tend to form dermal scars in healing wounds, scars that are believed to preclude blastema production. Wound healing around the margins of rabbit ear holes is uniquely characterized by the development of prominent epidermal downgrowths adjacent to the severed sheets of dermis in the integument on either side of the ear. If these downgrowths act as epidermal blockades preventing scar formation in favor of allowing blastema cells to accumulate, a logical approach to the experimental induction of regeneration in normally nonregenerating mammalian appendages would involve manipulation of the mechanisms by which epidermis heals amputation stumps.