130 S. R. Pelc 



ic"RpAt r 



d=. , ^,^.: .., e(a^tA+b)_e-^T(aA+b+bAT) reps (16) 



^a-j-Dt jA L J 



When the organism is killed for preparation, i.e. T=t, 

 equation 16 can be shortened to : — 



kB 



d= 



(a+bt)A2 _ 



e^t(aA+b)-(aA+bAt+b) 



reps (17) 



When the element can be assumed to have decayed com- 

 pletely in the organism, i.e. T=oo, e"^^=0. 



kBe^* 



These equations will at once give the appropriate expres- 

 sions for constant concentration when b=0, and for concen- 

 tration proportional to time when a=0. 



(b) Exponential increase or decrease of concentration 



f(T)=be'^^ 



^^K^e — (g(a_A)T_i) reps (19) 



a— A 



kR 



forT=t:d=— ^ (l-e^^-'^H) reps (20) 



a — A 



for T=oo, a solution which is valid only where (a — A) is 

 negative: — 



kBe(^-«)t 



d= r — reps (21) 



a— A 



The solution for concentration proportional to l-e""'' can 

 easily be computed by combining the solutions given under 

 (a) and (b). 



(c) Concentration increasing at first and then decreasing 

 through excretion, etc., similar to Fig. 1. 



