CHILD, CHARLES MANNING

born Feb. 2, 1869, Ypsilanti, Mich., U.S. died Dec. 19, 1954, Palo Alto, Calif. American zoologist who developed the axial gradient theory of regeneration and development, a physiological explanation of the ordered re-creation of animal parts following an injury. While at the University of Chicago, where he spent his academic life (1895-1934), Child experimented extensively with invertebrates such as planarian flatworms and freshwater hydras, which show a remarkable ability to regenerate themselves from small fragments. He observed that characteristic parts, such as a head or a tail, usually grew from that portion of the fragment where the same part had previously been joined, a phenomenon known as polarity. On the basis of his experiments, Child advanced a theory of antero-posterior dominance, stating that physiological activity in a multicellular organism increases along its axis from bottom to top (or tail to head), and that this gradient of activity in a tissue fragment determines the position of structures growing from it. He felt that the gradient was caused by the action of a chemical factor on cell functions. Among his publications are Individuality in Organisms (1915) and Patterns and Problems of Development (1941).