. Journal of radiology . ll see these are markedlyless. Figure 4 is a picture of theaction of the homogeneous gammarays from a milligram of radium Page Nine PHYSICAL ACTJON OF RADIUM studied in much the same way asis the beta radiation, omitting theaction of the factor F. This place-ment of the radium is not verydifferent from that actually usedin treatment and it gives us achance to compare it with the betarays. We see that owing to thegreat penetrating power, the gam- AND X-RAYS—LOEB by the cylinder has been reducedto 3/1,000 of its value at the sur-face. At nine milimeters below thesurface
. Journal of radiology . ll see these are markedlyless. Figure 4 is a picture of theaction of the homogeneous gammarays from a milligram of radium Page Nine PHYSICAL ACTJON OF RADIUM studied in much the same way asis the beta radiation, omitting theaction of the factor F. This place-ment of the radium is not verydifferent from that actually usedin treatment and it gives us achance to compare it with the betarays. We see that owing to thegreat penetrating power, the gam- AND X-RAYS—LOEB by the cylinder has been reducedto 3/1,000 of its value at the sur-face. At nine milimeters below thesurface the ionization has beenreduced to 25 per cent of its valueat the surface, while 5 per centof the total number of ions formedin the cone have been formed attins point. The total number of Ionization b\i Gamma T^ Iotv* lt\ Cone. = Icm«, p«.r cc ptr Sec. Htst c^mTn = , Zt7o OS \ Va\ ToK\ Ion* To\ttn«A HtuSO^oVToto-l IcXi LTV Co-nt s x. 10 o< r*Vtu\ <*<)?<: «* lo^ To*™...!. ma rays can go through 82 centi-meters before having produced 99per cent of the ionization they arecapable of producing in the this distance the ionization overthe cylinder has been reduced1/1,000,000 of its value, due tothe inverse square law and the ab-sorption. At centimeter, 50per cent of the ions formed in thecone have been formed and theionization below the area cut out ions formed in the cone by thegamma rays is about X Io11ions per second. The ionizationin the first 9 millimeters of depthis at the rate of X io9 ionsper cubic centimeter per is seen that while the total ioni-zation for gamma rays is slightlygreater than that due to the betarays in the whole cone the ionsformed in the first cubic centime-ter are about 1/20 of the number Page Ten PHYSICAL ACTION OF RADIUM AND X-RAYS—LOEB formed by the beta rays. Thatmeans in order to produce thesame effect at the surface withgamma rays the treatment wouldhave to be 20 times
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