198 OF THE NERVE CURRENT. 



thesis of the existence of a peculiar power, or of some 

 new mode or form offeree not yet discovered.* It is at 

 least not improbable that the varying effects noticed 

 in connection with the nervous system may be deter- 

 mined by alterations in the intensity of the current, 

 and in the conducting properties of the fibres, instead 

 of being due to the transmission of different 'kinds of 

 nerve force. One would have thought that it would 

 be more in accordance with the doctrines of physical 

 science to endeavour to explain the phenomena by the 

 action of forces we know something about, than to 

 attribute them to the influence of other forms or modes 

 of force which are purely fanciful and fictitious. At 

 any rate it will be time to call in the aid of such airy 

 nothings when all attempts to explain the facts by 

 known forces shall have failed. 



But it is interesting to notice how often minds 

 of the most rigidly physical tendencies seize upon 

 purely conjectural hypotheses, and use them as if 

 they were established truths. It has been surmised 

 that nerve action depends upon a chemical change 

 which is supposed to take place in every part 

 of the nerve fibre. Mr. Herbert Spencer settles the 

 question in the most summary way by boldly assert- 

 ing that the axis cylinder of a nerve consists of some 

 colloid " matter isomerically transformed with ease." 

 He accounts for nerve action by suggesting that the 

 protein substance of the axis cylinder " is habitually 

 changed from one of its isomeric states to another," 



* Physicists and chemists see no difficulty whatever in as- 

 suming the existence of many modes of force of which they can 

 form no conception, and think it very satisfactory to refer phe- 

 nomena which they cannot understand to some at present 

 undiscovered form or mode of ordinary motion ; but if any one 

 attributes these same phenomena to the influence of some 

 equally undiscovered form of force having no connexion what- 

 ever with primary energy or motion, he is ridiculed, because, 

 say the physicists and chemists, " there must be unity in 

 kosmos !" 



