BOOK REVIEW SOUL MADE FLESH The Discovery of the Brain -- and How It Changed the World. By Carl Zimmer. Illustrated. 367 pp. New York: Free Press. $26. In the beginning soul was everywhere -- in fire, air, earth and water. There were ''tongues in trees, books in the running brooks, / Sermons in stones, and good in everything.'' The human impulse to anthropomorphize, to explain the workings of nature in human terms, was irresistible. As scientific culture took shape, the spiritual, anthropomorphic element of nature was beaten back. Anima -- the breath of life, the soul -- was chased...