42 Mr. Martyn J. Roberts on the Analogy between 



suffusion in the act of blushing was shown when the action was 

 viewed as analogous to or identical with electric phaenomena. 

 I now proceed to consider this analogy as displayed in reflex 

 action, premising that at present the heads merely of the theory 

 are given, reserving for a future occasion the development of 

 the subject in its fullest details. Theories are often condemned 

 without a hearing by some who pride themselves upon being 

 mere practical men, to such with all due respect I will quote 

 the words of a learned author: "Where a definitive explanation 

 of phaenomena is yet impossible, an hypothesis which is not op- 

 posed to the facts, but on the contrary accords with them and 

 which opens a new field for research, is admissible even in an 

 exact science founded upon facts." 



32. We may consider reflex action as merely motion ex- 

 cited in muscles by irritation of sensitive or incident nerves in 

 these or adjacent parts, and that sympathetic action is motions 

 referrible to the same cause. All these reflex motions, whether 

 of the sympathetic or other parts of the system, appear to me 

 to bear the closest resemblance to electric induction, and that 

 the current in the sensitive and incident nerves induces an ac- 

 tion in the nerves of motion that lie contiguous to them. 



S3. Suppose A A to be a wire through which a current of 



electricity can be passed, and that 



A————— —————— ——A another wire, B B, placed close to 



P ^ B the first forms part of a closed cir- 



cuit that is offering a perfectly con- 

 tinuous path for the transmission of the electric fluid ; then if 

 a current be passed through A A in the direction of the arrow, 

 it is found that at the moment of the first passage of the 

 current it creates or "induces" another current in B B, and 

 in a direction contrary to the primary current in A A; but 

 this secondary or induced current is only of momentary dura- 

 tion, no trace of its existence appearing after the first instant 

 of passage during the whole continuance of the primary cur- 

 rent; nevertheless the moment we annihilate the current in A A 

 a new current is induced in B B, but in an opposite direction 

 to the first induced current. Such are some of the phasno- 

 mena caused by the action of a current of electricity upon neigh- 

 bouring conductors, and such also there can be no doubt is 

 the action of nervous currents upon nerves contiguous to others 

 conveying these currents. 



34. It will be seen that one condition necessary to the pro- 

 duction of these phaenomena in wires by electricity, is that of 

 a perfect continuity for conduction in the channel conveying 

 the electric fluid ; for if the wire B B be broken no current 

 can be induced in it; and I think it will be found 



