LIVING TORPEDOS IN BERLIN. 



483 



and where consequently the organ-current can be excluded by 

 leading off from skin and organ from points in a line which is 

 isoelectrical as regards the shock and the organ current. In the 

 torpedo the polar surfaces of the organ preparations are covered 

 with skin, and if on the one hand, the leading-off is from one of 

 these surfaces, on the other hand, from the lateral surface or from a 

 transverse section of the preparation, the organ-current of the 

 length of the columns included between the two leading-off points 

 is always present in the circuit, and any possible electromotive 

 actions of the skin can only be determined by elimination : this 

 can, however, be accomplished in the following manner. 



In Fig. 1 9 an organ preparation is represented : at V\i is bounded 

 by the ventral skin, and at 

 D by the dorsal. The curves 

 1-6 represent different posi- 

 tions of the galvanometer 

 circuit, the terminals of 

 which are formed by the clay 

 points of the unpolarisable 

 conducting tubes, and in 

 which equilibrium is main- 

 tained by the circular com- 

 pensator for the purpose of 

 measuring the electromotive forces. The point m divides the length of 

 the preparation as nearly as possible in half; the points d f y d^ and v', v l 

 lie as close as possible to the dorsal and ventral skin respectively 1 . 



In all the cases, organ-current force is present in the circuit, and 

 besides this, in the cases 2, 4, 6, any electromotive action of the 

 skin that there may be. If the dorsal points are shifted from d'> d t 

 to D, or the ventral points from v', v l to V, then not only is the 

 skin taken into the circuit, but also the tract of the columns between 

 the points is slightly increased. If the skin is electromotively 

 inactive, then the removal of tf, d l to D as well as of v', v l to V 

 must result in a slight strengthening of the positive organ-current 

 force, and this must be the same in both cases if the preparation is 

 of regular columnar arrangement, and if the additional-column 

 tracts are the same length. On the other hand, a deviation from this 



1 The adjustments mV, mD had been investigated by Eckhard, who did not 

 find electromotive action here any more than between V and D in the organ at rest. 

 (Beitrage zur Anatomic und Physiologic, vol. i, Giessen, 1858, 4, pp. 161, 162. Comp. 

 i. pp. 204, 210.) 



I i 2 



6 



Fig. 19. 



