REVERSED POLAR EFFECTS IN LIVING TISSUES 211 



through the action of the distal kathode make and the 

 proximal anode-break. 



The firefly under natural conditions emits flashes of light 

 at intervals of about three seconds, from two discs, situated 

 on the ventral surface of its tail. 



We select a specimen and make suitable electrical con- 

 nections, one with the head, and the other with the luminous 

 disc. The natural luminescence of the insect is moderate 

 and intermittent; but on now passing through it a descending 

 current from a battery having an E.M.F. of twelve volts, the 

 light at once becomes persistent and very brilliant. We 

 must bear in mind that the luminous discs stand here in the 

 place of the terminal motile indicator, of the neive-and- 

 muscle or Mimosa preparation, and that the state of excitation 

 is indicated in them by the increase of luminescence instead 

 of by an excitatory movement. This glow-response, then, is 

 due to the action of the proximal kathode-make. The induced 

 brilliance slowly dies down, and in the course of a minute and 

 a half becomes very feeble. If the circuit be now broken. 

 a single intense flash is produced, due to the excitation of 

 the distal anode-break. The insect now recovers from the 

 state of induced excitation, and begins once more to exhibit 

 its natural intermittent flashes. We next pass the current 

 in the reverse, that is to say ascending, direction. The light 

 again becomes persistent and brilliant, owing to the excitatory 

 action of the distal kathode-make. During the continuation 

 of the current, the light wanes and becomes feeble. But when 

 the circuit is broken, there is once more seen a single flash of 

 intense light, due to the action of the proximal anode-break. 



In order to ensure a simpler condition for experiment by 

 eliminating the nervous conduction of excitation, I next 

 isolated the double disc, and found that the detached organ 

 maintained its excitability for a couple of hours or more. 

 The discs now emitted a light which was somewhat feeble 

 but not intermittent. Electrical connections were then made 

 with the two discs, by means of fine cotton threads, moistened 

 with saline solution, and an E.M.F. of sixteen volts was used. 



P 2 



