216 INJURY, RECOVERY, AND DEATH 



It may be remarked that the turgidity of the cells 

 affords good indication of their condition. It is easily 

 tested by lifting them partly out of the solution; if 

 turgid they appear stiff, otherwise they collapse or 

 appear flaccid. It is, however, necessary to distinguish 

 between loss of turgidity in isotonic or hypotonic solu- 

 tions, which indicates injury, and a similar appearance 

 in hypertonic solutions, which may indicate nothing of 

 the sort. In the latter case the cell promptly recovers 

 its turgidity when placed in tap water; in the former 

 it does not. 



Another criterion of injury is afforded by the appear- 

 ance of the chlorophyll bodies. In the normal cell they 

 are arranged in regular rows and are of a clear trans- 

 parent green color. Where injury occurs they lose their 

 regular arrangement and the color becomes more opaque. 



In 0J05 M Ca (N03)2 the cells live for a week or more. 

 During the first few days, at least, penetration is not 

 more rapid (perhaps less so) than in a balanced solution. 



Similar results were obtained with other salts. 



The outcome of these direct tests is therefore an 

 unqualified confirmation of the results obtained by the 

 indirect methods. We find that penetration in injurious 

 solutions is relatively rapid as compared with penetration 

 in non-toxic solutions. This corresponds to the fact that 

 recovery from plasmolysis is more rapid in injurious 

 solutions as well as to the fact that conductivity increases 

 in such solutions. 



It would therefore seem that we may regard deter- 

 minations of electrical conductivity, and, in some cases, 

 of recovery from plasmolysis as reliable means of detect- 

 ing alterations in permeability. It is, however, desirable 

 to go further, if possible, and analyze the factors involved 

 in electrical resistance. 



