The emperors, both as public officials and private philanthropists; the prelates of the official Church and the monastic leaders; the lay aristocrats and, for many centuries, the professional healers, all have sought to found medical institutions. These have been purposed to provide consolation and help to the lower and middle social class. Philanthropic institutions have taken special measures to aid the sick, the crippled, the blind and the elderly poor. Byzantine sources indicate that hospitals were usually vital components of the city social network. The hospital administrators, whom the Byzantine sources call xenocfocfro/, were originally members of the clergy. By the tenth century the physicians have taken considerable control over the therapeutic practices in the hospitals. Professional medical assistants and nurses, the hypourgoi, were helping the doctors in curing the sick. The hospitals in the years of the Byzantine Empire have greatly contributed to the development of medicine, which, throughout this period, displays originality and innovation.