246 Mr. J. J. Woodward on the Modern 
be, there is a group of easily repeated elementary experiments 
which seem to show pretty distinctly that whatever the ner- 
vous impulse may be itis not merely an electrical current. 
It was known already when Haller wrote * that a string 
tied tightly around a nerve, although it in no wise interferes 
with the passage of electrical currents, puts a speedy end to 
the transmission of nervous impulses. With this old experi- 
mental difficulty uncontradicted, it seems strange that any one 
should declare at the present time that “the main objection 
raised to the electrical character of nerve energy is based upon 
its slow propagation” f. In fact this latter objection is alto- 
gether a subordinate difficulty which may perhaps be entirely 
explained away; the main experimental objection does not 
relate to the velocity, but to the conditions of the propagation 
of the nervous impulse. If instead of tying a string around 
it the nerve be merely pinched or bruised well with a pair 
of forceps, so as to destroy its delicate organic texture, if it 
be compressed tightly by a tiny, metallic clamp, if it be 
divided by a sharp knife, and the cut ends brought nicely into 
contact, or brought into contact with the extremities of a piece 
of copper wire, it will still conduct electrical currents as well 
as ever, but can no longer transmit the nervous impulse. So, 
too, there are certain poisons, such as the woorara, which 
completely destroy the capacity of the nerve for transmitting 
nervous impulses without in the least diminishing its conduc- 
tivity for electricity {. 
In view of these and other practical difficulties, the best 
instructed modern physiologists no longer attempt to identify 
the nervous impulse with the electrical phenomena by which it 
is accompanied. Du Bois-Reymond himself has suggested that 
the nervous agent “ in all probability is some internal motion, 
perhaps even some chemical change, of the substance itself con- 
tained in thenerve-tubes, spreading along the tubes” §. Herbert 
Spencer came to the conclusion that “ nervous stimulations and 
discharges consist of waves of molecular change” || flowing 
* A, von Haller, ‘Klementa Physiologiz,’ lib. x. sect. viii. § 15, t. iv. 
(Lausanne, 1762), p. 880. He cites as authority the essay of Le Cat, 
crowned by the Berlin Academy in 1753. [We have in the S. G. O. 
Library the Berlin edition of 1765, ‘Traité de lexistence &c. du fluide 
des nerfs,’ &c. | 
+ Barker, p. 8, op. cit. supra. 
{ Claude Bernard, ‘ Legons sur la Phys. et la Path. du Systéme ner- 
veux’ (Paris, 1858), t. i. pp. 157 and 224. 
§ Translation of a lecture given by E. Du Bois-Reymond at the Royal 
Institution, London, in Appendix no. 1 of H. Bence Jones’s ‘Croonian 
Lectures on Matter and Force’ (London, 1868), p. 180. 
| Herbert Spencer, ‘The Principles of Psychology,’ vol. i. (New York, 
1871), p. 95. Compare also his ‘ Principles of Biology,’ vol. ii. (New 
York, 1867), p. 346 et seq. 
