446 LIVING TORPEDOS IN BERLIN. 



median and outer edges of the organ ; the functional activity of 

 preparations cut from the same organ at short intervals of time is 

 for unknown reasons very different ; and in addition to this there 

 is the variable amount of short circuiting caused by the remnants 

 of cut columns which remain attached to the uninjured ones (see p. 

 440). These are the reasons (indicated on p. 418) why even that 

 small degree of exactitude with which I was obliged to content 

 myself in muscles and nerves, cannot be attained in polarisation 

 experiments on the Torpedo columns themselves. A table of the 

 secondary electromotive effects of the electrical organ similar to the 

 ones which I drew up for muscle and nerve, with double entry, in 

 which one head should comprise increasing current densities with 

 currents in both directions, another head increasing closing times, 

 could only be thoroughly carried out by someone who, like Boll at 

 Viareggio, has at his disposal for weeks together at least five freshly 

 caught fish daily, and who has no other object in view 1 . 



In what follows the secondary electromotive effects will be 

 especially dealt with, which the current induces either in the 

 direction of the Torpedo-shock or in the opposite direction. The 

 former, according to the nomenclature employed by me in my book 

 on Gymnotus, I call absolutely positive, the latter absolutely nega- 

 tive 2 . Polarisation in the direction from belly to back is therefore 

 absolutely positive ; and according as it follows an absolutely posi- 

 tive or negative polarising-current it may be considered relatively 

 positive or negative. For the sake of greater facility in distinguish- 

 ing polarising-currents with respect to their direction, I will call 

 the current in the direction of the shock the HOMODROMOUS, and 

 that in the opposite direction the HjETERODROMOUS 3 . The homo- 

 dromous current is indicated by an ascending arrow ( f ), the hete- 

 rodromous by a descending one ( j ). Plus and minus signs serve 

 to distinguish between relatively positive and negative polarisation. 

 By 'both currents,' I understand simply the homodromous and 

 heterodromous currents. Finally for brevity, it is desirable to call 

 the polarisation whether through the homodromous or the hete- 

 rodromous current, whatever its absolute direction may be, as 

 relatively homodromous and heterodromous polarisation. 



1 Archiv fur Anat. und Physiol., 1873, p. 77. 3 Loc. cit. pp. 149, 213. 



3 A colleague learned in philology whom I consulted with regard to these expres- 

 sions, advised the use of ' isodromous ' and ' anisodromous.' I considered, however, 

 the forms introduced into the text more practical on account of the similarity of sound 

 of the others to ' isotropous ' and ' anisotropous ' which are used in the description of 

 the organ. 



