OF THE ELECTRICAL ORGAN OF TORPEDO MARMORATA. 
501 
There is a possible source of fallacy connected with the nature of the preparation. 
The skin may have electromotive properties, and electromotive changes may follow its 
injury. The subject has been investigated by du Bois-Reymond, but without any 
decisive results (23). It would appear, however, that if the skin is electromotive it 
is only feebly so, and any change from the skin must, in blocks of organ, be swamped 
by the larger organ-current. Experiments were, however, made upon the subject at 
Arcachon which showed that in the injured skin the surface becomes negative to the 
deeper uninjured parts. We should, therefore, expect that injury of the dorsal skin in 
the case of an immersed block of tissue would cause an electromotive change opposing 
that of the organ, whilst similar injury of the ventral skin would cause a change 
favouring that of the organ. If this be so, then in the case of a strip of organ with 
skin remaining on its dorsal and ventral surfaces, which has been totally immersed in 
hot water, the total electromotive change is that of the plate’s organ-current plus 
that of the ventral skin minus that of the dorsal skin; the skin effects, one opposing 
and the other favouring the total organ effect, thus balance each other. But, if a strip 
be cut and the organ-current allowed to subside, injury to the dorsal skin only should 
be followed by sinking of the difference, injury of the ventral skin only by rise of the 
difference. The following experiments justify this view. In a strip 25 turns, long and 
3 nuns, in width and breadth, examined one hour after preparation, the difference 
between dorsal and ventral surfaces was + ‘0021 R. The strip was now held up 
by its ventral skin, and the dorsal skin allowed to touch a hot surface. On examining 
the difference, it had diminished to — '0008 R. The same strip was now held up by 
its dorsal skin, and the ventral skin was allowed to touch a hot surface : the difference, 
when examined, had increased to -f- 002 R. Finally the whole strip was immersed in 
hot water for two seconds, when the difference was found to be + '0225 R. 
In another strip, cut from a small Torpedo, and measuring 13 millims. in length, the 
difference 15 minutes after preparation was found to be + '002 R. The dorsal skin 
was now carefully removed, and the contacts were made upon the ventral skin and the 
dorsal ends of the columns respectively. The difference had diminished to + '0015 R. 
The ventral skin was carefully cut off, the contacts now being made upon the 
uncovered ends of the columns, and the difference found to be + '0027 R. In the 
operation of removing the skin it is difficult to avoid injuring the organ columns ; such 
injury would always produce a + effect, which would have to be taken into consideration. 
It seems, then, that in the injured skin the surface becomes negative to the unin¬ 
jured deeper parts. It is, therefore, not improbable that the very small currents 
observed in entire Torpedoes are, to a large extent, skin currents, these being pro¬ 
duced by the injuries which the skin must receive in the process of capture, handling, 
&c. ; but the question is one which demands further investigation. It is obvious that 
it does not affect the present inquiry. 
An “ organ-current ” may be reproduced in a strip of tissue 24 hours after the 
preparation of the strip. Thus a block of organ was cut from a medium-sized 
