VI PREFACE. 



closing of external currents are modified by the excitatory 

 influence of the nerve-current, and how impossible it is to judge 

 of or interpret these effects correctly without taking this 'in- 

 terference ' into account. It is to be noted that Prof. Bering is 

 led by his observations to a conclusion as to the nature of the 

 opening contraction, which, although by no means identical with 

 that arrived at by Tigerstedt and Griitzner, is in intelligible 

 relation with it. 



The second Part begins with three independent investigations 

 of the same subject by three of the most distinguished living 

 physiologists the first by Prof, du Bois-Reymond, of Berlin; 

 the second by Prof Hering, of Prague ; the other by Prof. Her- 

 mann, of Zurich, now of Kb'nigsberg all of which were published 

 within a few months of each other. The purpose of du Bois' 

 paper is to give a more full account, based on new experimental 

 investigations, of the phenomena which the author discovered 

 many years before and designated by the term 'positive polarisa- 

 tion.' In muscle and nerve there are, according to him, two 

 kinds of polarisation, of which one is identical with physical 

 polarisation of porous bodies steeped with electrolytes, the other 

 is purely physiological, that is, peculiar to living excitable 

 structures. As it manifests itself in muscle and nerve, positive 

 polarisation consists in this, that when either of these structures 

 is traversed axially by a voltaic current of very short duration, 

 the galvanoscopical after-effect observed on opening, instead of 

 being, as in ordinary polarisation, opposed in direction to the 

 led-in current, is in the same direction with it, varying according 

 to the density of the external current and other well-defined 

 conditions which need not here be referred to, but exhibiting 

 throughout the most intimate association with the functional 

 activity of the organ. 



A few months later in the year in which du Bois presented 

 his Memoir to the Berlin Academy, a communication on the 

 same subject was submitted to the Academy of Vienna by 

 Hering, in which he described the same phenomena under 

 another designation, the main fact being that when a current 



