Charles Manning Child (1869-1954): the past, present, and future of metabolic signaling.

Charles Manning Child's work focused on metabolic gradients and their influence on organismal development. Early in the 20th century, his work had considerable currency, but by the second half of the century he had become little more than a historical footnote. Yet today Child's ideas are once again topical. While there were issues of cause and effect that Child and his students were never able to address adequately, in hindsight the extent of his eclipse hardly seems warranted. In fact, the demise of Child's theories may have resulted from larger changes in the nature of biology in the early 20th century. Child frequently studied planarians, hydroids, and other animals that are capable of asexual, agametic reproduction, and his theories most clearly apply to such organisms. In contrast, Thomas Hunt Morgan, initially one of Child's competitors in studies of regeneration, later developed the field of transmission genetics based on fruit flies, which can only reproduce via gametes. Child's theories and model systems were largely casualties of the success of Morgan's mechanistic paradigm. Nevertheless, in modern biology metabolic gradients, recast in terms of redox signaling, have become central to understanding both normal and pathological development. (c) 2005 Wiley-Liss, Inc.