NTEeweaell THE HUMAN SPECTROMETER I. Introduction ~C.E. Miller During the past six months, the HumanSpectrometer has been devoted largely to the study of certain features of Cs!9" fallout and its uptake by humans. Thus, the gamma-ray body activities of 11 subjects from Cen. tral and South America and of 7 Marshallese have been measured and the trend of cesium burden of our control subjects has been brought up to date In addition, extensive measurements have been made of the Cs!37 contents of filter papers collected from an air monitoring program dating back to 1953. The radium body burdens of two former dial painters have been de termined. Studies of the relationship between total and exchangeable K in humans have been started. The gamma-ray spectrum emitted by the liver of a Tridacna clam collected in the Bikini lagoon is given. The low-energy, gamma-ray background of the Iron Room hasbee: reduced by about 20 per cent with the | addition of 1/8 in. of lead to the floo and one wall. es “ ty Be, II. In Vivo Measurements of Cs!37 a ‘Son, C.E. Miller and L. D. Marinelli te te, Me nk ay act UE ae gus net fu ae Cs}37 Trends in Humans at aot igt ae 2 curves were plotted have been re~examined in the light of subsequent experience. Figure 18 consists of new curves based on these data in- corporating the following changes and additions. Ge (1) The January, 1956, point on the CEM curve has been dropped The data had been determined using a 4-in. by 4-in. Nal(T1) crystal on loan from the Harshaw Chemical Company through the courtesy of E. C. Stewart. This point hadbeen incorrectly plotted since the crystal efficiency factor for the standard 4-in. by 14 in. crystal was used. 9012121 "ee A a Because of its obvious importance, all pertinent data from which these a & bee Bet PRY The build-up of Cs/97 as a function of time in four control subjects was reported in graphical form in the preceding Semiannual Report. (1)