A Theory of Growth Limitation

Abstract

The theory of growth limitation discussed in this review holds that animals continue to grow by the proliferation of voltage-producing units until, by the summation of these units, whether segments or cells, a critical inhibitory voltage is built up. The formation of these units occurs in distal growing regions, and it is in such terminal zones that the inhibitory voltage finally attains a critical value. Subsequent growth of the segments and of the cells of which they are composed, is usually very great, but it is primarily by cell enlargement, not by cell proliferation. This theory is based on the facts uncovered by a systematic reinvestigation, on a scale never before attempted, of posterior regeneration in an earthworm. It is also supported by a large number of anatomical, bioelectrical, and biochemical facts contributed by previous investigators. These are discussed, together with the relationship of this theory to theories of nutritive competition and of hormone action in the control of growth. In b...