LIVING TOBPEDOS IN BERLIN. 467 



two pairs of electrodes and joined together again, no effect was 

 produced by tetanising it. 



I made a similar experiment on the nerve marked R I. in the 

 Table, and obtained with a deflection of 52 sc. (Helmholtz' arrange- 

 ment) negative results as follows : 



With a distance of coil of loomm. the deflection was o, 



* 5 2 



25 SBC.; 



that is to say, a variation of T V When a woollen thread steeped 

 in sea-water was substituted for the nerve no effect was seen. So 

 far everything was regular, but it is strange that both Christian! 

 and I observed, in addition to the regular negative variation, a quick, 

 positive, initial jerk, and I twice saw a similar terminal jerk, so to 

 speak. These positive jerks of the mirror could not be attributed 

 to errors in the arrangement (such as escape of current, action 

 at a distance or the like), because they were observed first by 

 Christiani and then by me, after half a year's interval of time and 

 with altogether different apparatus, and because no effect occurred 

 when the nerve was divided, or when a moist woollen thread was 

 substituted for it. Whether this indicates some peculiarity of 

 electrical nerves must be decided by further investigations. However 

 this may be, with regard to this unexpected collateral effect and 

 with regard to the search for the supposed fundamental errors of 

 experiment, an observation was neglected (a failure which will now 

 be repaired), viz. that of the propagation of the variation in two 

 opposite directions in a nerve acting purely centrifugally. Corre- 

 sponding observations were afterwards made by me on the spinal 

 nerve roots of the frog \ 



3. Wectrotonus currents in the Electrical Nerves of the Torpedo. 



In the investigation of electrotonus currents in electrical nerves, 

 Christiani also met with irregularities, which for the present can 

 be ranged under no certain law, and which require further researches 

 for their explanation. In the fourth right nerve of the fish killed 

 on the 1 3th of December, the total length of the three tracts being 

 10 mm., I observed with from one to five Groves in the electrotonis- 

 ing current, that the anelectrotonic and kathelectrotonic augmen- 

 tations appeared regularly, the first rising up to a certain point and 

 then gradually diminishing, the latter sinking immediately. When 

 the nerve was divided and brought together again between the 



1 Untersuchungen iiber thierische Elektricitat, ii. pt. i. p. 589. 

 H h 2 



