232 INJUEY, EECOVEEY, AND DEATH 



a fourth, the nuclear surface, which does not agree in 

 behavior with any of the others.*"* It is quite possible 

 that there are other surfaces within the cell which likewise 

 differ in their behavior. 



If we suppose that these surfaces not only differ among 

 themselves, but that their permeability fluctuates under 

 normal circumstances, we shall probably get a fairly cor- 

 rect picture of the complex relations which obtain in the 

 cell. This conception is not as simple as that of the 

 "reaction chamber" hypothesis of Hofmeister,**^ but it 

 agrees more nearly with our present knowledge.**^ 



The conception that the cell contains a variety of mem- 

 branes which are capable of alterations in permeability, 

 is capable of explaining some important phenomena. 

 Among these may be mentioned certain effects of injury. 

 It is well known that mechanical injury is followed by 

 increased respiration:®^ this may be explained by the 

 increased permeability of membranes which have pre- 

 viously kept the oxidizable material from being attacked. 

 Increased respiration due to chemical agents'** might be 

 explained in the same way. 



An illustration of a different reaction is the bitter 

 almond, which evolves HON upon injury. In this case a 

 glucoside and an enzyme are brought together when 



»»Osterhout (1913, D). 



"Hofmeister (1891). 



" It may be added that while changes in the permeability of internal 

 membranes may affect the electrical conductivity of cells which are 

 filled with protoplasm (as in the case of most animal cells) they can 

 hardly play an important role in cells like those of Laminaria (and most 

 plant cells) in which the interior of the cell is occupied by a large central 

 vacuole. In the latter, however, the permeability of the vacuole mem- 

 brane must be of importance. 



"Cf. Czapek (1913-20); Tashiro (1917). 



"For recent investigations see Brooks, M. M., (1918, 1919, 1920, 1921, 

 A, B); GuBtafson (1918, 1919) ; Haas (1919, A, B) ; Irwin (1918, A, B) ; 

 Thomas (1918). 



