The Central Intelligence Agency conducted a 14-year program to find ways to control human behavior" through the use of chemical, biological and radiological material, according to agency documents made public today by John Marks. The documents ... suggested broader experimentation on unwitting humans by the intelligence agency or its paid researchers than had been publicly known before. Mr. Marks distributed 20 documents that described the following incidents, among others: In 1956, the C.I.A. contracted with a private physician to test "bulbocapnine," a drug that can cause stupor or induce a catatonic state, on monkeys and "convicts incarcerated at" an unnamed state penitentiary. A letter from an unnamed C.I.A. official in 1949 discussed ways of killing people without leaving a trace. "I believe that there are two chemical substances which would be most useful in that they would leave no characteristic pathological findings," the letter said. In 1952, two Russian agents who were "suspected of being doubled" were interrogated using "narcohypnotic" methods. The two men were given sodium pentothal and a stimulant. One interrogation produced a "remarkable" regression, the papers said, during which "the subject actually relived certain past activities of his life. The subject totally accepted Mr. [name deleted] as an old and trusted and beloved personal friend whom the subject had known in years past in Georgia, U.S.S.R." The C.I.A. conducted secret medical experiments from 1949 through 1963 under the code names Bluebird, Artichoke, MK Ultra and MK Delta.