CHAPTER XIX 



THE LEAF CONSIDERED AS AN ELECTRIC ORGAN 



Electrical organs in fishes Typical instances, Torpedo and Malepterurtis 

 Vegetal analogues, leaf of Pterospermwn and carpel of Dillenia indica or 

 pitcher of Nepenthe Electrical response to transmitted excitation Response 

 to direct excitation Uni-directioned response to homodromous and hetero- 

 dromous shocks Definite-directioned response shown to be due to differential 

 excitability Response to equi-alternating electrical shocks Rheotomic ob- 

 servations Multiple excitations Multiplication of terminal electromotive 

 effect, by pile-like arrangement, in bulb of Uriclis lily. 



IT has been shown that by a study of the peculiarities of 

 electrical response in plants, it is possible to obtain an 

 insight into the obscurities of similar responses in the animal 

 tissue. Among animal structures, there is one the elec- 

 trical organ of certain fishes the explanation of whose action 

 offers unusual difficulties to the investigator. But I shall 

 attempt to show in the course of the present chapter, that 

 there are also, on the other hand, vegetable structures, the 

 study of which will be found to elucidate the electro-motive 

 action here involved. Taking that of the Torpedo as type, 

 we find that the electrical organ is disposed in the form of 

 columns, each column consisting of numerous electrical 

 plates, arranged in series, one over the other, like the plates 

 in a voltaic pile. Each electrical plate consists of a rich 

 plexus of nerve-fibres imbedded in a gelatinous mass. 

 There are thus two surfaces, one nervous and the other non- 

 nervous. Each disc then becomes electro-motive under the 

 impulse from the nerve. Though the induced electro-motive 

 force in each plate is small, yet in consequence of their serial 

 arrangement in columns, the elements are coupled for inten- 

 sity, and the resulting E.M.F. of discharge becomes high. 



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