166 



Dr. N. H. Alcock. The Electromotive [Dec. 15, 



" The Electromotive Phenomena in Mammalian Non-medullated 

 Nerve." By K H. Alcock, M.D. Communicated by A. D. 

 Waller, M.D., F.E.S. Eeceived December 15, 1903,— Eead 

 February 25, 1904. 



(From the Physiological Laboratory of the University of London.) 



Up to the present time there would appear to have been no published 

 researches on isolated mammalian non-medullated nerve, and indeed, 

 except for the paper of Brodie and Halliburton,* all our knowledge of 

 these nerves has been either by inference from similar nerves in cold- 

 blooded animals or derived incidentally from experiments undertaken 

 for a different object. 



When it appeared, therefore, that the technique for mammalian 

 medullated nerve served equally well for the non-medullated, f it 

 became a matter of interest to examine the phenomena displayed by 

 the latter, and the very evident advantages of dealing with nerves of 

 considerable size and comparative longevity, and the possession of a 

 ready standard of comparison in the medullated nerves of the same 

 animal, greatly assisted in obtaining an exact result. 



• Methods. 



The splenic nerves were found to be very suitable objects for this 

 purpose. They consist almost entirely of non-medullated fibres, £ 

 and in the horse, which is the animal which has been used for 

 these experiments, the various bundles form a plexus around the 

 splenic artery, which can be separated by careful dissection into its 

 component parts, giving isolated pieces of nerve 1 — 1*5 mm. in 

 diameter and from 6 — 8 cm. in length. These pieces will commonly 

 retain their irritability for several hours if kept in 1 ■ 05 per cent, salt 

 solution at 18° C, into which they are placed from a quarter to half 

 an hour after the death of the animal. Waller 7 s§ galvanographic 

 method was employed as well as the capillary electrometer. [| 



In the experiments on the negative variation, the exciting current 

 was derived from an accumulator of large capacity, in order to secure 

 the greatest possible constancy, and the excitation was maximal, except 

 in Experiment 716. The temperature at which the experiments were 



* Brodie and Halliburton, ' Journ. of Physiol.,' vol. 28, p. 181. 

 f ' Eoy. Soc. Proc.,' February, 1902, p. 264. 



X The proportion of non-medullated to medullated fibres varies in different 

 animals ; sections made from the nerves actually used showed that medullated 

 fibres formed less than 0*5 per cent, of the total number. 



§ Waller, " Signs of Life," 1903. 



|| The analysis of the electrometer records will be considered at a future time. 



