Arsenious acid is in daily use for destroying the nerve-filaments in a tooth-pulp before filling the cavity, and it is still considered one of the best agents for the purpose. It is true that violent symptoms have sometimes followed its use, which always needs caution: still osteitis and its accompanying pain might occur after any destructive application, and we may fairly consider that 1/50 gr., especially when combined, as it usually is, with a little morphia, is free from any serious risk of arsenical irritation.