from the elements deposited in the body (especially in the bone) is small compared to the external radiation. But it may give a considerable amount of injury during the long period since it will continuously irradiate the important organ, namely the marrow. It is therefore necessary to observe carefully the clinical development in the future. For this purpose, it is important to measure and analyze the quantity of radioactivity in the urine, The study is now being proceeded from this viewpoint. In order to discharge the fission products deposited in the bones, EDTA(Ethylene diamine tetra acetic acid) can be used which however is not very efficient. It is reported that in an animal experiment about 20% of the substaces were discharged when EDTA-Na and EDTA-Ca were applied alternatively in an early stage of deposit. In our case, too, it may be possible, using EDTA, to discharge the fission products several times faster than otherwise. Since EDTA-Na, being poisonous, cannot be used to the human body, we are now trying to use EDTA-Ca. lh. About the Hygienics of the Environment and the Food: (i) The Boat as the Living Place — As is discussed in the section of the physical properties of the ashes, the half-life of the fission products on the Fukuryu Maru was changing from time to time. 8 days at March 17 and 20 days at April 22. decreased to about 20% of that of March 17. It was about By this time, the intensity also On April 22, the intensity of radiation in the boat ranged from 2 mr/hr to 20 mr/hr. It may not be very long before the intensity becomes less than the permissible dose 1.8 m/hr, As is seen from Table 5, the measured intensity for t - ray alone and the total intensity of both f= and y - rays are not very different. This may be understood as the result of the distance between the measuring instru- ments and the é- ray sources, the absorption of considerable amount of C - rays by the wooden parts of the boat into which the radioactive substance soaked, and the penetration of extra y- rays from remote sources through the ceilings and the walls. The radiation has an effect on so that the amount of injury should It is not appropriate to use the GM from one to the other is not simple the human body through the ionization be measured by the miliroentgenmeter. -counter. The conversion of results either, There are many boats besides the Fukuryu Maru on which the ash fell when they were making voage several hundred miles off Bikini. The count of radioactivity on these boats varies from hundreds to ten-thousands by the Gi-counter. But the intensity is at most 3 mr/hr when measured at a distance of 5 cm by the miliroentgenmeter. Since the intensity at 50 cm is only one-hundredth of the amount at 5 cm, it may have hardly any effect on the human body. The amount of radioactivity on these boats is there- fore very small and trivial compared to the case of the Fukuryu Maru. How- ever, if the radioactivity is present at all, it may have a chance of getting into the body through the mouth, skin or lung. Of course, it is better not to be exposed to the radiation, however a bit it is. It is -6-