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W. J. V. OSTERHOUT 



it is in sound condition and also to foretell approximately how 

 long it will survive if subjected to the conditions of the laboratory. 

 Having established an empirical standard for healthy tissue it 

 is possible to compare quantitatively the condition of any sample 

 of tissue with this standard. This has great practical value for 

 such researches as are here described, for it enables us to reject 

 unhealthy tissue at the outset. 



It also has a high theoretical value, for it proves that the perme- 

 ability of a tissue is a delicate and accurate index of its vitality, 

 and in view of this all agencies which affect permeability acquire 

 a special significance. And it emphasizes in the most striking 

 way that the preservation of the normal permeability of the 

 plasma membrane is of fundamental importance to the organism. 



