Experimental Production of Functioning Reduplications—a Triple and a Function- Ing Quintuple Hindlimb in the Frog

EXPERIMENTALLY produced functioning reduplications, triple and quintuple hindlimbs of the frog have not yet been described. Supernumerary limbs can be produced either by transplantation methods or by the methods described in this paper. In order to prevent confusion between a reduplication of the primordium itself and a doubling after orthotopic transplantation of a limb bud, the author distinguished (1925) (i) reduplication of the limb primordium and (ii) pseudoreduplication consisting of an orthotopic transplanted limb of a donor and a regenerated limb of the host. This grouping was accepted by Smook (1934). In the following description the above-mentioned terms will be applied in the sense given. As this paper deals with supernumerary limbs of the primordium itself the present cases are more instructive for human and animal pathology than are the transplantation experiments. Reduplication of this kind reveals the biological potency of the limb primordium as realized in abnormalities such as sometimes develop in man and animals. Another problem dealt with in the present paper is a neurological one. The function of the triple and quintuple reduplications indicates some remarkable capacities of the central nervous system acting upon these multiple primordia since their earliest embryonic development. There will be given in this paper a short preliminary record only of the function; further details will be published later of the movements after they have been studied by cinematography.