SELECTIVE PERMEABILITY 81 



An organism injured by exposure to 

 a toxic solution may recover if it is re- 

 turned to the normal environment be- 

 fore the injury has progressed too far. 

 But if injury has gone beyond a certain 

 point, the recovery may not be complete 

 and the organism may remain in a state 

 intermediate between normal health and 

 a moribund condition. 



This is of especial interest, since in 

 physiological literature it seems to be 

 generally assumed that when recovery 

 occurs it is always complete, or practi- 

 cally so, as if it obeyed an "all or none" 

 law. But it is evident that partial re- 

 covery may be easily overlooked unless 

 accurate measurements can be made. 

 This fact serves to illustrate the im- 

 portance of quantitative methods in the 

 study of fundamental problems. 



These studies have led to the develop- 

 ment of equations which enable us to pre- 

 dict with a satisfactory degree of accuracy 

 the recovery curves which are observed 

 under a great variety of conditions. 



