484 LIVING TORPEDOS IN BERLIN. 



behaviour under these circumstances is to be attributed to electro- 

 motive action of the skin. 



Such a deviation in fact shows itself with great uniformity, so 

 that on passing from I to 2 (from md f to mD) on the back, a con- 

 siderable increase of the positive force, and on passing from 3 to 4 

 (from mi/ to mV) on the belly, a less considerable weakening of the 

 positive force is observed. The latter result cannot proceed from 

 increased length of the column tract. On the other hand, both 

 results are fully explained, by assuming that the skin is feebly posi- 

 tive in comparison with the interior. At first sight, one might be 

 inclined to attribute the fact that the enfeeblement on the belly is 

 less in amount than the increase in strength on the back, to differ- 

 ent electromotive character of the pigmented skin of the back and 

 of the pigmentless skin of the belly, which is however not demon- 

 strable with certainty in the case of the frog 1 . Another ground of 

 explanation, less remote, and which makes no fresh supposition 

 necessary, is that the increase of strength of the organ-current, due 

 to the greater length of the column tract between the points, adds 

 itself to the skin action on the back and deducts itself from that on 

 the belly. 



The first experiments were made with the last summer fish (IV). 

 In a successful experiment I obtained 



in the curve I (wwf) + 0.0057 Eaoult. 



2 (wD) + 0-0103 



( + 0-0049 



30*0 5 + O ' oo6 3 



(Mean + 0-0056 ,, 



( + 0-0034 



4(F) ] * - 02 9 



(Mean + 0-0032 



Thus the increase in strength on the back at the removal of md' 

 to mD amounted to 0-0046, the diminution in strength on the belly 

 at the removal of mv' to m V, in accordance with what has been said 

 above, amounted to only about the half, 0-0024. Let x be the 

 difference of potential between the skin and the interior of the 

 organ, 8 the force of the column tract between the skin and the 

 points lying next to it, then we have on the back. 



0-0057 + 8 + x = o-o 103, 



1 Untersuchungen, etc., vol. ii. part ii. p. 14. 



