Civilization is a particular kind of culture, characterized by increasing complexity in social, economic, and political organization, a settled life, a food supply in excess of subsistence levels, occupational specialization, writing and reckoning, and innovations in the arts and sciences. Mesopotamia, the land between the Tigris and Euphrates Rivers, was the arena of the growth and decay of many civilizations, including those known as Sumerian, Chaldean, Assyrian, and Babylonian. Egyptian civilization has fascinated travelers and scholars since the fifth century bce when the Greek historian Herodotus initiated the tradition of Nile travelogues. One of the most peculiar uses of Egyptian mummies was the medieval practice of grinding mummies into a powder used in the treatment of wounds. Paleopathologists have subjected mummies to x-ray examination, computerized tomography (CT) scanning, electron microscopy, chemical analyses, immunological evaluations, and other analytic techniques that provide significant data with minimal damage.