or 0.01 lie per ml., was placed in series 

 of 4 tubes and in contact with the outside 

 surfaces of the skin. The sea water in the 

 beakers in contact with the inside surfaces 

 increased slightly in radioactivity from pas- 

 sage of the isotope through the skin. The 

 average of the percentage equilibrium 

 reached between the two solutions after 2, 

 4, and 6 days is shown in table 1 . 



Ruthenium -106 did not pass through the 

 fish skin to any great extent. Equilibrium 

 was 17 percent complete at 6 days. There 

 appeared to be a passage of a small amount 

 which was not increased appreciably with 

 time . 



There is no information on the ruthenium 

 content of natural sea water Undoubtedly it 

 is extremely small . There was, therefore, 

 an increase in the total ruthenium outside the 

 tubes. 



.01 uc, .05 ,uc, and 0.25 ,uc of strontium-89 

 per ml . 



Tne activity at the skin surface varied 

 in the different observations . There was 

 of course more radioactivity in the deeper 

 muscles when solutions of higher specific 

 activity were employed. The results of 

 measurements of penetration can best be ex- 

 pressed as the percentage of the radioactivity 

 of the skin found in the tissue underneath. 

 Table 2 gives the relative radioactivities of 

 the muscle layers when the activity at the 

 skin surface due to the Sr-89 is considered 

 as 100 percent . 



There was a gradual diffusion of the iso- 

 tope through the tissues, the specific activity 

 in the tissues gradually increasing with time. 

 However, this diffusion was relatively slow 

 only a very small percentage was present in 

 the deep muscles after 8 days . 



Ruthenium salts are quite insoluble in 

 v/ater . With the addition of ruthenium tri- 

 chloride to the sea water there was consider- 

 able hydration. It is doubtful if there was 

 much ionic ruthenium outside the membrane 

 and there were particles present as a fine 

 precipitate . The ruthenium -106 gradually 

 leaves the sea v/ater and is adsorbed on var- 

 ious surfaces after such an addition as was 

 made in these tests. 



Cesium- 137 



Similar experiments to those carried on 

 with strontium-89 were completed with 

 cesium -137. The pads were soaked in solu- 

 tions containing . 1 ,uc and 1 ,uc cesium -137 

 per ml . Observations were made of the 

 radioactivity of the tissues under the skin 

 after 2, 4, and 8 days and the results are 

 presented in table 2. 



PENETRATION OF ISOTOPES INTO 

 THE MUSCLE TISSUES 



Strontium -89 



Three series of experiments with ob- 

 servations made in duplicate were performed 

 in which pads soaked in sea -water solutions 

 of Sr-89 were placed against the skin of the 

 fish and the radioactivity of the tissues under- 

 neath were measured. Strengths of solutions 

 in which the pads were soaked varied in their 

 specific activity. The solutions contained 



Although the cesium- 137 solution was 

 carrier -free, there was an appreciable 

 amount of cesium added to the sea water in 

 relation to that normally present. There 

 was likely, therefore, a gradient from the 

 skin inward. 



The results of the experiments using 

 cesium -137 show a very marked entry of 

 cesium -137 into the fish body and diffusion 

 into the muscles underneath . After a short 

 time the muscle tissues contained consider- 

 ably more of the nuclide than was present at 



