1. (a) This work taken in part from a dissertation presented by RBL in partial fulfillment of the requirements for the Ph.D. degree, Indiana University, 1971.
2. (b) U. S. Public Health Service, Fellow, 1969–1971.
3. (c) Author to whom correspondence should be addressed.
4. (d) Present address: Western Electric, Box 900, Princeton, N. J., 08540.
5. For several fine examples of quantitative work, see other chapters of this book.