THE MECHANISM OF INJURY AND RECOVERY. 



By W. J. V. OSTERHOUT. 

 {From the Laboratory of Plant Physiology, Harvard University, Cambridge.) 



(Received for publication, June 20, 1920.) 



During the process of death the electrical conductivity of many- 

 tissues undergoes a change in electrical resistance by means of which 

 the process may be followed with considerable precision. This may 

 be utilized to measure injury and recovery.^ 



An illustration of this is seen in Fig. 1, which shows the gradual 

 fall in resistance^ of Laminaria placed in 0.52 m NaCl.^ After an ex- 

 posure of 5.2 minutes the resistance has fallen to 94.6 per cent of the 

 resistance it had in sea water.* If the tissue is then replaced in sea 

 water the resistance rises (uppermost dotted line) and returns to prac- 

 tically normal value. This rise of resistance may be spoken of as 

 recovery. 



^ Attention has been called in a previous paper (Osterhout, W. J. V., /. Biol. 

 Chem., 1915, xxiii, 67) to the need of accurate determinations of toxicity and 

 to the use of electrical measurements for this purpose. 



- For convenience in making comparisons the death curves used in a former 

 paper (Osterhout, W. J. V., Proc. Am. Phil. Soc, 1916, Iv, 533) are employed as 

 standards. Since in the recovery experiments the death curves vary somewhat 

 (depending on the temperature, the condition of the material, etc.), it is permis- 

 sible for comparative purposes to make the death curves coincide with the stand- 

 ard in as far as this can be done by multiplying the abscissae by the proper factor 

 (which is always the same for all the abscissae of any particular recovery curve). 

 This has been done throughout the experiments: otherwise an accurate com- 

 parison of the recovery curves would be difficult. The corrections made are 

 relatively small, since, in order to make the results comparable, all experiments 

 showing a wide deviation from the standard curves were rejected. Since the devia- 

 tions are chiefly due to differences in temperature the chief result of the corrections 

 is to make all the reactions appear as if they had taken place at the same 

 temperature. 



^ All the solutions had the same conductivity as sea water. 



* For convenience all results are expressed as per cent of the original resistance. 



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