242 PHYSIOLOGY ov MUSCLK- AND .VEUVES. 



non-magnetic iron may at any time be transformed into 

 a magnet, maki s the involved conception quite natural. 

 It i< exactly the same in the case of the electric organs 

 of the torpedo. The fact that they, though in them- 

 selves electrically inoperative, become electrically oper- 

 ative under the influence of the nerves, when c- >ml lined 

 with what we know of nerves and muscle, naturally 

 leads us to suppose that electromotive forces are pre- 

 sent in the electric plates, but that they are so ar- 

 raiM'ed as to cause no observable differences of tension 



D 



on the outer surface. Under the influence of the ac- 

 tive nerves, the particles endowed with electric forces 

 undergo a change in their relative position, differenco 

 of tension between the two surfaces of the electric plates 

 inter\ene, 'ind, as all the electric plates in an organ act 

 in (lie same way, the result is a powerful electric shock, 

 which, in spite of its powerful effect, differs from the 

 negat ive variation of the muscle- and nerve-currents only 

 as does the powerful current of a many-celled galvanic 

 batterv from the weak current of a small apparatu-. 



In order to make the similarity between the electric 

 organ on the one hand, and muscles and nerves on the 

 oih.-r. yet more prominent, we will carry the compari- 

 son with magnetic phenomena yet further. In fig. 65, 



IS \ 



I'll;. (')."). M Ai.M I 1C 1MMC Tl<>\. 



.1 // isa piece nf M>|'I iron. .V N ;i magnet which we bring 

 from some distance toward the in.u rod .1 />'. The result 

 is to evoke magnetism in J II. A becoming a north pole, 



and />' a .-oitth pole. Now, let i;< snppo>e that the non- 

 magnetic iron rod .1 I! i> replaced by an entirely similar, 



