Difference In Bacilli. It was stated In n pajor read boforo bo-foro tho National Association for tho Study and Prevention of Tuborculosls that human tuberclo bacilli possibly vary In vlrulonco in dlfforont patients. Ton bacilli havo beon found sufficient to Infect a guinea pig In somo Instances, In-stances, nnd In othors 100 hnvo boon found nocossary. Immunity in animals ani-mals may bo obtalnod by tho injection of Increasing numbers of tuberclo bacilli, ba-cilli, boglnnlng with ono or two and cautiously increasing the numbor from n culturo, tho minimum fatal dose of which Is nbout 100, or by tho Injection Injec-tion of, say, 100 or 200 bacilli of a virulent culturo to causo n local loslon which can bo cut out, preliminary pro-cautions pro-cautions having boon takon to prevent tho spread of infection.