Electromotive Phenomena of Non-iiiedull'ited Nerve. 379. 



'Observations on the Electromotive Phenomena of Non-medul- 

 lated* J^erve." By Miss S. C. M. Sowton. Communicated 

 bv Dr. Waller, F.E.S. Eeceived March 8,— Read March 29, 

 1900. 



[Plate' 4.] 



Ktihne and Steiner in their work on the olfactory nerve of the pike,t 

 published in 1880, showed that the laws of electromotive action in 

 meduilated nerve, as formulated by Du-Bois Eeymond, held good in 

 the case of non-medullated fibres. Having demonstrated the resting 

 current in a suitably prepared olfactory nerve, they proceeded to com- 

 pare the value of this current with that obtained from meduilated 

 nerves of the same fish as well as from the sciatic nerve of the frog. 

 The result showed a much higher E.M.F. for non-medullated than for 

 meduilated nerves, their diameter , being about equal ; a result con- 

 firmed by Biedermann and others working on the non-medullated 

 nerves of Anodonta. 



Ktihne and Steiner found that the resting current diminished rapidly, 

 but a new transverse section restored it to, and in some cases even 

 augmented, its original E.M.F. 



On stimulation with induction currents, a negative variation of high 

 value was obtained. The response was unfailing while the nerve was 

 fresh, provided that the stimulating electrodes were not applied too 

 near the peripheral end of the nerve where its character becomes 

 modified. 



While working at Leipzig during the early part of 1899, Professor 

 Hering was good enough to suggest that I should use the nerve which 

 had given such good results in the hands of Ktihne and Steiner for a 

 further study of electromotive phenomena in non-medullated nerve, 

 ^nd especialty with reference to the occurrence in such fibres of the 

 ^' positive after-variation " which his own researches! and those of 

 Head§ had made familiar in the case of meduilated nerve. Hering 

 had himself occasionally observed this effect in 1885, while using the 

 olfactory nerve for experiments on electrotonus. The positive after- 

 effect occurred most frequently on mechanical stimulation of the nerve 

 by cutting, more rarely it followed when induction currents were used. 



In the present experiments, the pike used ranged from l^to 2J kilos. 



* " Jfon-meduUated " is used in its ordinary sense as applied to grey nerve, and 

 without prejudice to the conclusions of Gad and Hey mans that such nerves may 

 be slightly myelinated, conclusions which Ambronn and Held have confirmed by 

 means of their " optical method." ' Archiv fiir Anat. und Physiol.,' 1896, p. 210. 



t K. und S. * Untersuchungen des Physiol. Instituts der Universitat Heidelberg,* 

 Bd. 3, p. 149. 



X ' W. S. B.,' vol. 89, 3 Abth., p. 137. 



i ' Pfliiger's Arch.,' vol. 40, p. 207. 



