"They make it look so clean," says Yoshio Shinozuka, holding a photo of a model of the torture chamber where he once worked. "It was dirty and dark and bloody." Only 16 when he was sent to Japan's infamous Unit 731 in World War II, Shinozuka helped doctors study the effects of diseases like anthrax and plague on prisoners in occupied China. Often they dissected their victims - "logs," they called them - while still alive, without anesthesia. The Japanese killed perhaps 10,000 people here, and another 250,000 throughout China with biological weapons, including plague. After the war the US government gave Unit 731 scientists amnesty in exchange for their trove of data.