Roentgen equivalent man has been defined since 1976 as equal to 0.01 sievert, which is the more commonly used SI unit outside the United States. A number of earlier definitions going back to 1945 were derived from the roentgen unit, which was named after Wilhelm Röntgen, a German scientist who discovered X-rays. The acronym is now a misleading historical artifact, since 1 roentgen actually deposits about 0.96 rem in soft biological tissue, when all weighting factors equal unity. Older units of rem following other definitions are up to 17% smaller than the modern rem. One rem carries with it a 0.05% chance of
Wilhelm Filehne at the medical polyclinic. In 1876 he became an associate professor of pharmacology at Erlangen, and ten years later, was appointed a full professor of the same subject at the University of Breslau. In 1911 he was succeeded at Breslau by Julius Pohl. In addition to work in the field of pharmacology, he made contributions in his research of optical illusions, being known for his experimentation with a phenomenon known as a Zöllner illusion. The so-called "Filehne illusion" is the illusory motion of a stationary background when smooth pursuit eye movements are made across the stationary background. Wilhelm Filehne Wilhelm