456 



Permeability 



over the entire surface, while cells which are described below as in 

 poor condition had a mottled appearance, or the protoplasm ap- 

 peared to be slightly shrunken, or else the cells, when held be- 

 tween the thumb and finger, could be felt to lack the normal 

 turgidity. 



In each case the description of the cell was written down before 

 the test was made, in order to avoid subjective error. 



Besides these cells, which were taken as nearly as possible at 

 random, thirty-six other cells were chosen as being undoubtedly 

 healthy, and of these only one showed the presence of sulfate. 

 From experience it is possible, by inspection, to be almost al- 

 ways, though never absolutely, certain which cells are going to 

 show the presence of sulfate. 



From this it seems evident that sap of live and healthy Valonia 

 cells does not contain free sulfate in large enough quantities to 

 give a visible precipitate with barium chloride. It is also equally 

 certain that when the cell dies sulfate enters, and it follows from 

 this that the presence of sulfate in the cell indicates injury or 

 death, even though no other manifestations are visible. 



