The following tissues were taken: for rats, skin, muscle, bone, liver, stomach, gut, kidney, and lung (in post shot specimens); for birds, skin, muscle, bone, liver, gizzard, gut, and lung (in some specimens). proventriculus, Special care was taken in all dissections to prevent cross contamination between organs. The dissection instruments were washed and wiped after each step, and the digestive tract with its contents dissected out last to prevent general cross contamination by the more or less fluid digestive tract contents. Results. The specific activity of the organs and tissues of the rats is given in Tables 16a and 16b. In Tables 17a and 17b the disintegration rate for activity within the organs and tissues of the birds is given. Analysis of Organs and Tissues, Pre-shot. The amount of radioactivity found in the organs and tissues of rats and birds in the pre-shot collections is small (Tables 16a and 17a) with a maximum of 47 d/m/g in the terns and 26 d/m/g in the rats. However, there are similarities in the distribution of the activity according to the different tissues and organs of the rats and birds. In Figure 11, a histogram of the average a/m/g for the organs and tissues of all of the pre-shot birds and rats is given. Similarities in radioactivity levels for like organs or tissues in the birds and rats are apparent with gut, muscle, liver, skin, and stomach in both groups containing measurable amounts of radioactivity. In bone none was detected. If the ‘ergans and tissues are arranged in descending orderof average _ ~ 65 - aoe eM ,