SINCE THE DAWN OF time, the basic form of human interaction and endeavor has been one of hierarchy, with power and control focused on a central figure, be it a chieftain, king, or a religious, political, or military leader. Historically, in the practice of medicine and the healing arts, however, the most common pattern was the solo practitioner. In the mid-1800s, due to the expanding knowledge base of medicine, physicians started to aggregate into groups focused around university and religious hospitals. These medical groups also followed a classical hierarchy that has characterized academic, religious, political, and military organizations. A hierarchy (from the Greek hierarchia, the power or rule of a hierarch) .s defined as an organizational design wherein a group of individuals is arranged in order of rank, grade, or class, and is led by a hierarch. In turn, a hierarch (from the Greek heirarches, a steward or keeper of sacred things; hieros, sacred, archos, a ruler, from archein, to rule, lead) is the leader.