William P. Stiritz, who took St. Louis-based Ralston Purina Co. into new ventures and later helped scale it back down, will retire as chief executive later this year while staying on as chairman. The company said that it will split the CEO job between two longtime Ralston executives–W. Patrick McGinnis, 49, and J. Patrick Mulcahy, 53. Stiritz, 62, has been CEO of the St. Louis company since 1981.
