THE THEORY OF ELECTRIC ORGANS 271 



The sensitiveness of these leaflets is of that order which 

 requires on an average an E.M.F. of 12 volts to cause excita- 

 tion by kathode-make or anode-break. And this value is 

 considerably higher for anode-break than for kathode-make. 

 The lowest E.M.F. which I have found with highly excitable 

 Biophytum to be effective in causing excitation, was 4 volts, 

 and in less sensitive specimens it might be as high as 

 20 volts. 



Now, on applying a strong stimulus, say by contact of 

 hot wire, on the petiole bearing the sensitive leaflets, an 

 excitatory wave is initiated, which, during its progress, brings 

 about depression of the leaflets in serial order. After an 

 interval of about half a minute, a second wave is found to 

 be initiated from the original point of excitation, causing a 

 second series of responses, shown by the same serial depres- 

 sion of the leaflets as before. And such recurrent excitations 

 may take place from a single stimulus, as often as twenty times. 

 On determining the E.M.F. value of each of these excitatory 

 waves, however, I have found it to be of the order of 'Oi volt. 

 This, it will be seen, is only about four one-hundredths 

 of the minimum E.M.F. necessary to induce excitation of 

 the leaflet. It clearly follows that here the original stimulus 

 is the cause of these multiple excitations, and not the first 

 response the cause of the second. 



The phenomenon of multiple response then, is, as we have 

 seen, of very extensive occurrence, and not confined to elec- 

 trical organs. We have seen it exhibited even by ordinary 

 tissues, and we shall find in subsequent chapters that 

 such repeated responses are actually induced in nervous 

 and glandular tissues, under the action of an intense stimulus. 

 This is interesting in view of the fact that the electrical 

 organs of fishes are made up of either neuro-muscular or 

 neuro-glandular elements. 



