1903.] 



in the Nerves of Warm-blooded Animals. 



265 



but with regard to isolated nerves contradictory statements have been 

 made, and it was to ascertain if possible the reason of this discrepancy 

 that the present research was undertaken. 



Methods. 



The following method was employed in all the experiments here 

 quoted. The animal was killed by decapitation, and the body left 

 undisturbed for 30 — 45 minutes. The nerves were then dissected out, 

 placed in a 1 -05 per cent. NaCl solution at about 30° C, and kept at 

 this temperature for about half-an-hour or more. They were then 

 allowed to cool to room temperature (17 — 19° C), and it was found 

 that, as a rule, the negative variation of nerves so treated was of the 

 •order of 1 millivolt (vide infra). This, of course, is not an absolute 

 value of the true P.D. between active and inactive parts of nerve, but 

 -only a fraction of it, depending upon the amount of internal derivation 

 in a nerve trunk by indifferent conducting tissue. 



From about 2 to 6 hours post-mortem this value remains at a fairly 

 constant amount, for instance, in Experiment B d , the sciatic of the 

 rabbit was used 5 h. 30 m. post-mortem, and gave a negative variation 

 of 0*00083 volt; in Experiment A k , 2 h. 40 m. post-mortem the value 

 was 0*0007 6 volt, and these are typical instances. The table on p. 277 

 gives the result of twenty-two experiments, in which the values were 

 taken for heat determination, which illustrates this. 



Certain points may be here noted. The practice of placing nerves 

 in salt solution for some time before use has been employed by Waller,* 

 Ootch,t and Boycott, | in the case of the frog.§ 



The effect of changes in the composition of the salt solution is the 

 subject of another research which I hope to publish at a future time ; 

 however, I may here state that small differences in the concentration 

 of the solution — e.g., ±0*1 per cent. NaCl — make no apparent differ- 

 ence in the condition of the nerve, and the same is true in the main 

 of small differences in the reaction, and of small differences of tem- 

 perature. 



Waller|| has pointed out that the presence of lactose in the solution 

 is of advantage, and taking a greater value of the negative variation 

 for a sign of greater irritability, the same appears to be true in mam- 

 malian nerve for maltose and glucose, though I make the statement at 

 present with some reserve. 



For instance : — Experiments B tc and B td . 



* Waller, 6 Brain,' vol. 73, 1896, p. 43, et seq. 

 f Gotch, < J. Physiol.,' toI. 28, p. 32. 

 X Boycott, loc. cit. 



§ See also Grotch and Horsley, loc. cit. Macdonald and Reid, loc. cit. 

 jj Waller, loc. cit. (Lectures), p. 73. 



