CHAPTER XIII 



CURRENT OF INJURY AND NEGATIVE VARIATION 



Different theories of current of injury Pre-existence theory of Du Bois- 

 Reymond Electrical distribution in a muscle-cylinder Electro-molecular 

 theory of Bernstein Hermann's Alteration Theory Experiments demon- 

 strating that so-called current of injury is a persistent after-effect of over- 

 stimulation Residual galvanometric negativity of strongly excited tissue 

 Distribution of electrical potential in vegetable tissue with one end 

 sectioned Electrical distribution in plant-cylinder similar to that in muscle- 

 cylinder True significance of response by negative variation Apparent 

 abnormalities in so-called current of injury ' Positive ' current of injury. 



IF a section be made of an uninjured nerve or muscle, the 

 transverse contact will be found to be galvanometrically 

 negative, as compared with an uninjured longitudinal contact. 

 I shall have occasion in the present chapter to give a simple 

 explanation of this phenomenon and of the excitatory nega- 

 tive variation of the current of injury. It is, therefore, only 

 necessary to recapitulate briefly the three theories which have 

 hitherto been proposed on this subject. 



The Pre-existence Theory of Du Bois-Reymond supposed 

 that the smallest particle had the same electro-motive 

 characteristics as the entire tissue, each such electro-motive 

 molecule consisting of two bi-polar portions, the positive 

 poles of any two molecules being always face to face with 

 each other. This theory was based upon the fact that a 

 muscle-cylinder, for example, exhibited a peculiar distribu- 

 tion of electrical tension. There are in such a cylinder, one 

 longitudinal and two transverse surfaces. Midway in the 

 cylinder is the equatorial zone of the longitudinal surface, 

 and this zone is positive to all the rest. Thus the electro- 

 motive difference between one electrode placed on the 



