According to Hecker, the reason for the establishment of a 40 day period was that during the thirteenth and fourteenth centuries the fortieth day was generally considered the day of separation between the acute and chronic forms of disease. The Bible was also drawn upon to endow the number 40 with special significance. For example, the Flood lasted 40 days and other biblical episodes also extended over 40 days. The number 40 was likewise considered important in alchemy, for it was believed that 40 days were needed for certain transmutations.