LIVING TORPEDOS IN BERLIN. 533 



surfaces of the marginal columns, but would not have disturbed 

 the heterodromous current threads in their course through the 

 organ itself. The arrangement which does really exist, is superior 

 even to the insulating property of the cover of the individual 

 columns, for such a property would indeed oblige the currents, 

 between points of the lateral surfaces of all the columns, to take 

 their route along the column, but it would present no obstacle, 

 to the return of the currents from the dorsal to the ventral 

 surface, by the shortest route through the neighbouring columns. 

 On account of the tenuity of the connective tissue sheaths 

 of the columns, the proportion of the flow which equalizes itself 

 through them, instead of through the external conducting mass, 

 need not be taken into account, any more than that which 

 follows the course of nerves and blood-vessels. The irreciprocity of 

 conduction must be specially advantageous to the lower marginal 

 columns of the organ, the proper homodromous current of which 

 would otherwise be annihilated by the united heterodromous 

 current threads derived from the median columns, which are about 

 two-thirds higher and proportionally stronger. 



It deserves to be remarked, that on the assumption that the 

 shock is due to the marshalling of dipolar electromotive molecules 

 in the electrical plate, all that has been said about the whole 

 column may be equally applied to the individual molecule. Con- 

 sidering that the transverse section of the course of the homo- 

 dromous current in the molecule is infinitely small, the resistance, 

 notwithstanding the shortness of this course, is sufficient to 

 justify the application of the above conclusions to the molecule also. 



I endeavoured to give in the first communication an idea of 

 the configuration, in a transverse plane dividing the organs 

 about in half, of the system of current curves surrounding both 

 organs ; it is now necessary to alter this in consequence of irreci- 

 procity of conduction, but I do not venture to say anything more 

 decidedly about it. One thing alone is certain : the part of the 

 animal which lies between the medial edges of the two organs, viz. 

 its central nervous system, is, as was stated, in the course of the 

 strongest flow ; it will be traversed by even denser current curves 

 than was before supposed. The immunity of the Torpedo in regard 

 to electrical shocks (p. 432, 433), now an established fact, makes 

 the difference unimportant. 



What has been said here of the Torpedo, applies also essentially 

 to the Gymnotus and the Malapterurus. It was in studying the 



