(Original Caption) More than a month of continuous living in an underground room in Mammoth Cave was one of the hardships under taken by two university of Chicago physiologist to determine how easily man could adjust himself to a cycle of living different from the 24 hour day common to everyonr on the surface of the earth. Since June 4, they have been living on a 28 hour cycle, or a six-day week. The man are Dr. Nathaniel Kleitman and his assistant, Bruce Richardson. They expected to come up to the surface shortly. The men arise in the "morning" Richardson (left), washes, while Dr. Kleitman pours.