MUSCLES, NERVES, AND ELECTRICAL ORGANS. 1^ 



think I have before me in my rows of figures traces of what was 

 anticipated which can hardly depend on mere chance. 



Finally, it is to be noticed that it is not accurately understood 

 in what respect an ordinary experiment on positive polarisation and 

 an experiment on positive polarisation in conflict with tetanus differ 

 from each other. For in experiments without tetanus the muscle is 

 also in contraction during the passage of a short current. The time 

 has not yet arrived to examine this question. Perhaps the apparently 

 smaller positive polarisability of the tetanised muscle depends upon 

 the fact that the tetanus, which lasts longer than the closure of the 

 battery partly arrests the positive polarisation. 



13. On Secondary Electromotive Phenomena of Nerves. 



When I made a communication to the British Association in 

 Belfast, in the autumn of 1852, on secondary electromotive actions 

 of muscles and nerves (Sect. 7), I had not yet succeeded in obtain- 

 ing positive internal polarisation in nerves. In connection with 

 my hypothesis regarding electrotonus, and considering the fact 

 that muscles exhibit no extrapolar electrotonus, I then compared 

 muscle to hard steel and nerves to soft iron 1 . The middle tract of 

 a steel rod, surrounded by a coil through which a current is pass- 

 ing, becomes magnetic, and remains so after the cessation of the 

 current ; but it is only by action at a distance that the magnetism 

 spreads beyond the tract immediately involved. If the rod is 

 composed of soft iron it is magnetized throughout its length, 

 although with diminishing strength, from the coil to the ends ; 

 but after the cessation of the current the magnetism entirely dis- 

 appears. In the same way muscles and nerves then seemed to me 

 to behave differently in relation to the polarisation of their electro- 

 motive molecules. But I had theorised too soon. When in the 

 winter of 1852-53 I returned with improved apparatus to the in- 

 vestigation of secondary electromotive actions in nerves and muscles, 

 I found at once that nerves also possess positive internal polari- 

 sability or power of coercion (Coercitivkraff), in accordance with the 

 comparison just made, only that their polarisability is more difficult 

 to seize upon than that of muscles, for reasons that are easily 

 understood. 



From the great importance which this phenomenon appeared 

 to have in relation to the theory of electrotonus, I have since 



1 Untersuchungen, vol. ii. part i. p. 326. 

 O 1 



