INJURY, RECOVERY, AND DEATH, IN 

 RELATION TO CONDUCTIVITY AND 



PERMEABILITY 



INTBODUCTION 



SOME of the fundamental ideas of biology are most 

 difficult to define with precision. This is especially true 

 of such conceptions as life, vitality, injury, recovery, and 

 death. To put these conceptions on a more definite 

 basis it is necessary to investigate them by quantita- 

 tive methods. 



To illustrate this we may consider some researches 

 on the electrical conductivity of organisms. These ex- 

 periments show that the electrical resistance of a plant 

 or animal is an excellent indicator of what may be called 

 its normal condition of vitality. Injurious agents in- 

 variably change its electrical resistance. For example, 

 if the marine plant, Laminaria, is taken out of its normal 

 environment of sea water and placed in a solution 

 of pure Nad it is at once injured, and if the exposure 

 be sufficiently prolonged it is killed. During the 

 whole time of exposure to the solution of NaCl its 

 electrical resistance falls steadily until the death- 

 point is eventually reached; after this there is no 

 further change. A study of the time curve of this 

 process shows that it corresponds to a monomolecular 

 reaction (slightly inhibited at the start). This may 

 be expressed in the form of an equation which can be 

 utilized to predict the curve of death under various con- 



15 



