22.2 SECONDARY ELECTROMOTIVE PHENOMENA IN 



plate than for muscle and nerve. While negative polarisation quickly 

 disappears with increasing- time of opening-, like the internal polarisa- 

 tion of porous bodies, positive polarisation shows a persistence which 

 points to another kind of mechanism. It should not however remain 

 unnoticed that negative polarisation also persists a long time at the 

 junctions of saturated solution of sulphate of zinc, and physiological 

 solution of salt *. 



Although, then, traces of positive polarisation can be detected 

 for a long time in nerves and electrical plates which are dying at a 

 low temperature, it is more dependent on the vitality of the struc- 

 tures than negative polarisation. Boiling heat destroys it at once 

 and absolutely, although still leaving a remnant of negative polari- 

 sation ; and the destructive action of strong currents on polarisability 

 in general attacks principally positive polarisation. In addition to 

 this, the importance and bearing of the phenomenon may be inferred 

 from what has already been said as to its relation to the direction 

 of contraction, to that of innervation, and to that of the shock in 

 electrical fishes, as well as to its not less important relation to the 

 state of activity of the tissue. 



I do not think that any one trained in physics and who keeps 

 these facts before his eyes in their totality and in an unprejudiced 

 manner, will arrive at any other conclusion to-day than that to which 

 I was compelled to come many years ago. It is the conclusion not 

 that in positively polarisable structures electromotive forces having 

 the same direction as the primary current are generated, but that the 

 conducting molecules (Trtiger) of electromotive forces already existing 

 take the direction of the primary current. If to this it is added that 

 in the natural condition of the structures the electromotive molecules 

 are maintained by certain forces in a position, from which, although 

 they can be displaced by the weakest currents, they can be removed 

 permanently only by currents of a certain density, this simple and 

 natural assumption reconciles the known liminal intensity of positive 

 polarisation with the electrotonising properties even of the weakest 

 currents. It is unnecessary to mention that the great persistence 

 of positive polarisation agrees equally with this view. 



As I became acquainted with positive polarisation of muscle 

 shortly after the publication of my 'Preliminary Sketch' (1843), 

 and long before that of the first volume of the ' Untersuchungen ' 

 (1848), it is easy to see how I arrived at the conception of the 



1 Gesammelte Abhandlungen, vol. ii. p. 190. 



