Roentgen (unit) this derivative quantity the roentgen equivalent physical (rep) to distinguish it from the ICR roentgen. The introduction of the roentgen measurement unit, which relied upon measuring the ionisation of air, replaced earlier less accurate practices that relied on timed exposure, film exposure, or fluorescence. This led the way to setting exposure limits,and the National Council on Radiation Protection and Measurements of the United States established the first formal dose limit in 1931 as 0.1 roentgen per day. The International X-ray and Radium Protection Committee, now known as the International Commission on Radiological Protection (ICRP) soon followed with a limit of
Wilhelm Feldberg of the Royal Society in 1947 and made a Commander of the Order of the British Empire in 1963. Wilhelm Feldberg assisted many research workers who came to England as a part of their Commonwealth Medical Fellowship and Wellcome Research Fellowship. Under this Fellowships, Professor PN Saxena and Prof. KP Gupta of the Department of Pharmacology, Jawaharlal Nehru Medical College, Aligarh Muslim University, during the 1970s got many papers published together with Wilhelm Feldberg while their vocation at National Institute for Medical Research, Mill Hill. Feldberg's career was ended in 1990 when two animal rights activists gained access to his