496 
MR. F. GOTCH ON THE ELECTROMOTIVE PROPERTIES 
The difference between the two contacts is thus seen to be very small, and in four cases 
out of ten was opposite in character. It was evident that nothing could be made out 
with certainty as to the state of matters in the entire animal. On the other hand, the 
blocks of tissue which were cut from these and other animals for rheotome experiments 
never showed any such discrepancy. In these the difference was always such that the 
dorsal end of the block was positive to the ventral end. It is needless to give 
examples of this now, for the experiments which will be given will afford convincing 
proof of the truth of this statement ; hut it may be stated that in 45 instances 
in which the organ-current of a cut strip or block of tissue was observed and noted 
there is no instance of the current being otherwise than -}-, and that in all cases the 
strength of the current far exceeded that which was observed in the case of the entire 
animal. 
The difference observed very early in the work between the organ-current in the cut¬ 
out block of tissue, and that in the organ when in situ, suggested the view that the 
increased current found to be present in the former tissue was dependent upon the 
nature of the preparation — upon the fact that the piece of organ used was bounded by 
incisions. It was, therefore, determined to ascertain how far such incisions did affect 
the result. For this purpose the following experiment was carried out :—A medium¬ 
sized Torpedo, 18 centims. long by 12 wide, and 15 millims. thick at the median border 
of the organ, was fixed on a perforated vertical board ; the brain had been previously 
destroyed, but the other parts of the fish remained intact. The skin covering the 
dorsal and ventral surfaces of the right organ was now led off by kaolin plugs, 
the leading-off points being situated in the middle of the length of the organ, and 
5 millims. outside its median border ; and care was taken that the one electrode should 
be exactly opposite the other. The dorsal surface was found to be negative to the 
ventral; the difference of potential was, lioweve 1 ’, quite inconsiderable, and amounted 
to — ’001 R, ADULT. 
The organ, with its skin coverings, was now cut through a few millimetres in front 
of the leading-off electrodes. The direction of the cut was from without inwards and 
slightly backwards, and did not extend beyond the median border of the organ. On 
examining the tissue two or three minutes after the incision, the difference of potential 
was found to be the reverse of what it had been ; the dorsal contact being now positive 
to the ventral, the difference amounted to -j- ‘0005 It. 
A second cut was now made at right angles to the first cut, and thus nearly parallel 
with the long axis of the fish. It was external to the leading-off contacts, and 
extended through the length of the organ. The tissue now led off was, therefore, a 
long block bounded internally by the median border of the organ, anteriorly by the 
first cut, externally by the second cut, and posteriorly by the posterior boundary of 
the organ. The difference of potential was found to be still further increased after 
this incision, and amounted to + ’0015 R. 
T1 le left organ of the same fish was now taken, and a large wedge-shaped block 
