In a long-ago folk story an old man stands beside his grandson at the receding margin of the last ice sheet. Pointing back he says, "The edge was there when I was a boy." Today we live in an era of plenty. New techniques have vastly increased the scope of complex analyses and the celerity with which they are carried to completion. Generous public support has placed a variety of equipment in the hands of many workers. A few among us have been relieved from other duties for the single-minded pursuit of science; others not that fortunate have more leisure for research than ever before. As a result, facts are being uncovered in hitherto undreamed of abundance. Yet their synthesis still moves along like the glacier—grudgingly—a few miles to a human life span. Thus, this survey will prove more successful as an effort to present growth trends than for its integration of new knowledge.