MUSCLES, NERVES, AND ELECTRICAL ORGANS. 219 



several points, for on the whole a contraction wave will always run 

 from the middle of the muscle to its ends. In the sensory, arid less 

 certainly in the motor nerve-fibres, positive polarisation predominates 

 in the direction of physiological innervation. In the electrical plates 

 of the Malapterurus it predominates in the direction of the shock. 



Here it may be remarked, by the way, that there is no doubt that 

 the positive polarisation is the stronger, and not that the negative is 

 the weaker. If the polarising current density is but small, the 

 negative polarisation which is then alone present appears equal in 

 both directions. So also when exposure to a boiling temperature has 

 left, instead of both kinds of polarisation, only a small residue of nega- 

 tive polarisation in the organ, this is the same in both directions 

 just as it is in dying sensory roots. As it may therefore be con- 

 sidered proved that in electrical plates and in nerve roots it is the 

 positive polarisation which becomes stronger in one direction, not the 

 negative which recedes, we confidently apply the same explanation by 

 analogy, to the behaviour of both polarisations in the upper and under 

 halves of regular monomeric muscles, notwithstanding that a direct 

 proof for this explanation is still lacking. In all three structures 

 then muscles, nerves, and electrical plates positive polarisation 

 appears more strongly in the direction in which the physiological 

 process belonging to them whether contraction -wave, innervation- 

 wave, or electrical shock is propagated in them. This view, if further 

 verified, cannot be considered unimportant. For the possibility 

 already discussed (Sect. 18), that the preponderance of ascending 

 positive polarisation in the sensory roots may be only an action of 

 the physiological innervation-wave which is frequently propagated 

 in this direction, is rendered improbable by the necessity which it 

 involves of attributing the same action to three perfectly different 

 occurrences, the contraction-wave, the innervation-wave, and the 

 electric shock. 



In the endeavour to picture to oneself what takes place in each 

 of these three structures during polarisation, one is naturally inclined 

 to rank the negative polarisation in them with the internal polari- 

 sation of moist porous bodies. The idea at once suggests itself of 

 connecting the destruction of the internal polarisability of muscles 

 and of the electrical organ by boiling temperature, with the dimi- 

 nished resistance of the ' interstitial fluid l ', and to connect its 



1 ' Binnenfliissigkeit.' This is the name which Munk has proposed for the inter- 

 stitial fluid of moist porous bodies, so far as they indicate secondary resistance ; it 

 may also be applied to them as objects of polarisation (Archiv fur Anatomic, Physi- 

 ologie, etc., 1873, p. 254). 



