216 SECONDARY ELECTROMOTIVE PHENOMENA IN 



organ beginning to emit a peculiar stale odour. From a given 

 moment the actions generated by the descending current are in two 

 opposite directions. This is important, as it teaches that also in the 

 electrical organ these actions are the algebraic sums of two polari- 

 sations, a negative more transitory polarisation, and a positive which 

 subsides more slowly. 



At my suggestion, the late Dr. Sachs began some experiments in 

 Venezuela on the polarisability of the Gymnotus, the results of which 

 I have already published so fully from his note book, as well as 

 discussed in the * Untersuchungen am Zitteraal/ that I have nothing 

 to add to what has there been said 1 . I there showed that these 

 results may be satisfactorily deduced on the supposition that in the 

 organ of the Gymnotus, as well as in that of the Malapterurus, two 

 polarisations exist together, a positive and a negative, of which 

 the algebraic sum presents itself to observation ; and that there 

 also, the positive polarisation curve drawn relatively to the time of 

 opening is the less abrupt, while the negative is the more abrupt. 

 If Dr. Sachs never saw purely positive deflections, this is explained 

 only too certainly by a defect in his outfit and instructions, for 

 which I myself am to blame. He possessed only twenty small 

 Groves, of which three arrived broken, an accident on which I should 

 have calculated. Then I had not sufficiently impressed upon him, 

 because it had not been enough brought home to myself, that he 

 should use the smallest animals for these experiments and should 

 cut the thinnest possible strips from the organ. Considering the 

 exceptionally high liminal intensity which the electrical organ 

 possesses for positive polarisation, and which perhaps lies still 

 higher in the Gymnotus than in the Malapterurus, it is no wonder 

 that Dr. Sachs with seventeen Groves and a piece of the organ of 

 6-7 cm. transverse section, obtained no purely positive deflections. 



In the meantime, the discussion of Dr. Sachs' 'empirically 

 resulting ' curves supplied in some degree the lack of direct observ- 

 ation, as it left no reasonable doubt that both polarisations also 

 co-exist in the organ of the Gymnotus. Dr. Sachs also convinced 

 himself that boiling heat destroyed the polarisability of the organ. 

 Thus everything appears to take the same course as in the Malap- 

 terurus. Unfortunately, however, there is an important difference 

 between my experiments and Dr. Sachs' on another point. Accord- 

 ing to him, in the organ of the Gymnotus negative polarisation 



1 Loc. cit. pp. 205-221. The curves in Table II. of the work are, as will be easily 

 recognised, in our present mode of expression, polarisation curves drawn relatively to 

 the time of opening. 



