182 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Table 2. — Concentration of Cs'^^ in different tissues of 

 little tuna following a single oral dose 



Tissue 



Liver 



Heart 



Spleen „. 



Kidney 



Blood, wiiole 

 Blood serum. 



Muscle 



Gonad 



Bone 



Eye- 



Brain 



Skin 



Counts/minute/mg. after- 



1 day 



4,761 



3,214 



1,848 



1,643 



324 



322 



241 



285 



212 



159 



155 



164 



8 days 



1,358 

 821 

 821 

 499 



403 

 705 

 137 

 158 

 347 

 531 



Table 3. — Relative concentration of Cs"'' in tissues of three 

 species of marine fish 1 day after a single oral dose 



RETENTION 



Experiments were conducted in which whole- 



body retention of Cs'" by postlarval flounder and 

 the retention by certain tissues of croaker were ob- 

 served. Data were plotted against time on semi- 

 log paper as percentages of Cs'"' present at zero 

 time and analyzed by the standard kinetic ap- 

 proach usually applied to ftrst-order reactions 

 (Comar, 1955; Richmond, 1958). This procedure 

 need not be discussed here in detail, but a brief 

 description may facilitate presentation of the 

 experimental results. 



After fitting the curve to the retention data by 

 inspection, the slope of the linear tail was more 

 accurately determined by the method of least 

 squares and extrapolated back to the y axis or 

 zero time. The extrapolated values were sub- 

 tracted from the corresponding values of the com- 

 posite curve, and the differences were plotted on 

 an expanded scale for greater accuracy. The 

 linear tail of the new composite cm've was ex- 

 trapolated in the same manner, and the differences 

 between the extrapolated values and composite 

 values were plotted as before. This procedure 

 was repeated until the final subtraction produced 

 a straight line. 



Analysis of the retention process by this method 

 determines the number of exponential functions 

 involved, the rate of removal per unit time by eacli 

 function, and the amount of substance at zero time 

 represented by each rate function. It is not to 

 be inferred, however, that each function represents 

 removal from a single compartment, since there 

 may be intermediate steps involved or several 

 compartments may be contributing to a single 

 rate function. 



