The problem is to discover how amphibians are able to replace lost structures, such as limbs and tails, by regenerating new ones. Past work by a host of biologists has demonstrated the great importance of nerves entering a limb to a third of the normal number, then subsequent amputation is not followed by regeneration. The adult frog is unable to regenerate a limb after amputation. Nevertheless, when the hindlimb nerves are added, by appropriate deviation, to the forelimb so that the latter will possess the innervation of two limbs, subsequent amputation of this treated frog limb results in regeneration. Thus, we know that the quantity of nerves supplying a limb is of vital importance for its regeneration, but we still do not know how these nerves produce the essential stimulus for regeneration. Project Number 68.
Thornton, Charles S.
"Influence of Nerves on the Regeneration and Regression of Limbs in Amphibia,"
Jackson Hole Research Station Annual Report: Vol. 1957
, Article 15.
Available at: http://repository.uwyo.edu/jhrs_reports/vol1957/iss1/15