ON LIVING MALAPTERUKUS. 397 



of Malapteruras in the beautiful manner indicated by Mr. Gassiot 1 . 

 The above-mentioned spark-micrometer was so arranged that, in 

 place of the two platinum points which approached each other, two 

 copper wires bent like a swan's neck were used, from which gold 

 leaves hung down opposite each other. A glass case shielded it 

 from any draught. At a distance of 3 mm. from each other, the 

 movement of the leaves at the moment of the shock was doubtful. 

 At a distance of 2 mm. they obviously attracted each other. At a 

 less distance they flew together, a magnificent green flash appeared 

 and left the leaves fused together. It was then often possible to 

 tear them asunder uninjured by means of the micrometer screw, and 

 to repeat the experiment. 



Unipolar action, to be discussed in Sect. 3 of the following paper, 

 is concerned here. 



8. More detailed Investigation of the distribution of tensions 

 in the active organ of Malapterurus. The posterior half of 

 the organ acts more feebly than the anterior. The Equator 

 of the organ. 



It is the custom to speak of the polar surfaces of the electrical 

 organs. This is however a mistake, unless the organ is cut out of 

 the animal, raised into the air, 'and regardedas endowed with equal 

 electromotive forces at all points. As long as the organs are 

 under water, or are adjacent laterally to animal parts which have 

 similar relations as conductors, there can be no question of polar 

 surfaces in the strict sense of the word. If we represent such an 

 organ diagrammatically as a cylinder, the current curves now cut 

 the coat of the cylinder, instead of issuing only from its basal 

 surfaces. We may, nevertheless, speak of the polar surfaces of the 

 organ with the same accuracy as we do of those of a magnet, and with 

 this proviso we shall make use of this mode of expression. Minuter 

 details as to the special distribution of the discharge of the electric 

 fish will be found in my Collected Papers, No. XXX. 



1 On the attraction force manifested by the electricity of the Gymnotus electricus. 

 In the Transactions and the Proceedings of the London Electrical Society, from 1837 

 to 1840. London, 1841, 4. p. 197. Matteucci had described a similar experiment 

 on the Torpedo somewhat earlier. A wire supports the one gold leaf above the edge 

 of a metal disc, on which the fish lies. The other is suspended by a similar wire at 

 the edge of a metal cover put on the back of the fish. This cover is moved in order 

 to excite the fish, then the gold leaves may be seen to attract each other (Biblio- 

 theque Universelle, etc. Nouvelle Serie, 1837, t. xi. p. 392 ; Essai sur des Phe"no- 

 menes electriques des Animaux, 1840, p. 51, Fig. V; Traite", etc., p. 154, pi. III. 

 Fig. 27). It is difficult to comprehend how one can judge of the attraction of the 

 gold leaves, when one moves them one's self and moreover in the open air. 



