PHTSIOLOGT 49 



Although the protoplasm might not change the 

 final equilibrium it might prevent a true equili- 

 brium being reached by causing some substances 

 to enter so slowly that no true equilibrium would 

 be reached during the period of growth. 



The problem is a very complicated one and it 

 seems clear that we cannot hope to attack it suc- 

 cessfully without the help of careful quantita- 

 tive work. The studies here described are a 

 preliminary attempt in this direction. 



These studies lead me to look upon the semi- 

 permeable membranes of the cell as even more 

 important than I supposed. In certain cases it 

 seems quite possible that in a cell immediately 

 after death the same substances may be present 

 and the same reactions go on as just before it 

 was killed. But the difference between the living 

 and the dead state is very marked in respect to 

 the semipermeable surfaces: after death they 

 lose their selective power and the internal and 

 external solutions begin to mingle. When the 

 semipermeable surfaces no longer safeguard the 

 privacy of the chemical processes of the cell the 

 vital activities are unable to continue in. normal 



