A Theory of Growth Limitation

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Abstract
According to the proposed theory, animals continue to grow in their linear dimensions by the proliferation of voltage-producing units (cells or segments) until, by summation, a critical inhibitory voltage is built up. Subsequent growth may be very great but consists primarily of an increase in size of cells without proliferation or increase in voltage. Based on facts uncovered by a re-investigation on a scale never before attempted of regeneration in an earthworm, Eisenia foetida, this theory offers for the first time a physiological explanation of "Morgan''s law" that in all animals the rate of regeneration becomes slower as the anatomical level of regeneration becomes more distal. A possible biochemical mechanism is suggested in the relationship between electric and oxidation-reduction potentials. Old and new evidence that oxidizing potentials favor differentiation and inhibit proliferation and that reducing potentials do the reverse is reviewed. The relationship of such a theory to various nutritive and hormonal factors and to axial gradients is discussed. Hematopoietic and various epithelial tissues are excluded from the action of the inhibitory voltage. Bioelectrical and anatomical evidence regarding a self-produced inhibitory voltage is summarized and discussed.