Mummy in the Museo Egizio di TorinoThe Egyptians believed that the soul (ba) of a dead person could not survive in the hereafter if it could not return regularly to the body. Therefore, preservation of the corpse was deemed essential for survival. The earliest endeavours in this respect date to the Predynastic period, when bodies were already occasionally wrapped in linen and covered in resin. Such stiff hulls at least preserved an image of the body, even if the flesh itself decayed inside it. During the Old Kingdom, the Egyptians learned that the body had to be thoroughly dried first by using natron (a mixture of salt and sodium carbonate acting as an effective desiccant). Also, the first experiments were made with extraction of the internal organs. This became common practice in the Middle Kingdom, when also excerebration was sometimes performed. The heyday of mummification was during the New Kingdom and especially the Third Intermediate Period, when mummies sometimes received artifical hair and inlaid eyes and their shrunken flesh was stuffed with fillings under the skin. After that, the art of mummification declined and the embalmers increasingly relied on the excessive use of resinous mixtures. Mummification survived until early Christianity, when it was finally abolished because the adherents of the new religion believed in the supremacy of the soul over the body.