OF THE ELECTRICAL ORGAN OF TORPEDO MARMORATA. 
499 
A hot iron wire was now brought within a few millimetres of one of the cut sides 
of the preparation ; the difference immediately began to rise, as was shown on the 
galvanometer by a slow deflection amounting to more than 200 scale. On with¬ 
drawing the wire, the difference subsided ; on approaching it, it rose again. The second 
cylindrical block was examined in the same way half-an-hour after its preparation. 
The difference was found to be + '0017 It. One of the cut sides was now warmed as 
before, and the difference rose; when it had attained its maximum of rise it was 
compensated and found to be + ‘002 R. On withdrawing the hot iron wire it fell 
again, but on again bringing the hot wire near the cut surface it rose to + '0022 R. 
Similar results were obtained with the third cylinder, and could always be brought 
about in such preparations. In this respect, then, the organ-current resembles the 
demarcation-current of muscle and nerve. 
One of the most efficient methods for the production of a demarcation-current in 
the last-named tissues is that of making what is termed a “thermal section.'’ This 
method has the advantage of injuring the tissue locally without altering its dimen¬ 
sions to any considerable extent. It should be possible to produce similar thermal 
sections in the case of the Torpedo. From what has been said as to the structure of 
the electrical organ it is evident that the appropriate thermal section would be 
obtained if a block of tissue could be prepared which should consist of a few 
unimpaired columns surrounded by other columns partially in a state analogous to 
heat rigor. This was effected by the following simple plan :—A cubical block of 
tissue, consisting of several columns with their ends covered by skin, was held by its 
dorsal skin in the forceps, and then plunged in hot water so as to be wholly immersed 
for two seconds. On examining the block, the sides were seen to be opaque-looking. 
They were undoubtedly destroyed, but in the interior the substance of the columns 
appeared to be unimpaired. In such a block a thermal section has therefore been 
made on every plate and nerve branch within a millimetre or so of the surface. The 
resulting difference should therefore be very large, and investigation showed that this 
was the case. 
Three strips were cut from the organ of a large Torpedo. The first was cut from 
the median edge of the organ. The length of its columns was 55 mms., and the 
strip was 3 mms. in thickness and in width. It was immersed in hot water for two 
seconds, and then examined by leading off the skin covering the ends of the columns. 
The difference was found to be very large, amounting to as much as + ’052 R. 
The second strip was cut from the organ midway between its median and outer 
borders. Its length (23 mms.) was less than the previous one, owing to the columns 
being shorter at this point, but in other respects it resembled the first strip. On 
examining the difference two minutes after immersion it was found to be + '0336 R. 
A third strip was cut from the outer border of the organ, where the columns 
measured only 12 mms. in length. It was otherwise of the same dimensions as the 
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