OF THE ELECTRICAL ORGAN OF TORPEDO MARMORATA. 
495 
which he finds may equal •0000117 of a Daniell. No comparison is given between 
the current found to be present in the entire organ and that existing in the cut strip 
of tissue, from which it would seem that the different condition of the tissue in the 
two cases was considered as standing in no relation to the production of the current. 
My experiments show that, so far from this being the case with the tissues which I 
examined, there is a very marked difference between the organ-current shown by 
an entire organ and that shown by a cut strip. The galvanometer used in these 
experiments was a Thomson of high resistance, made by Elliott, which was brought to 
such a degree of sensibility that '0001 Raoult gave, with a resistance of 10,000 ohms 
in the circuit besides that of the instrument (5332 ohms), a deflection of 230 scale. 
By means of the compensator (described by Burdon Sanderson (22)) the organ- 
current could be “ balanced,” and the electromotive condition of the tissue thus 
measured. The balancing circuit was arranged in the manner described by the same 
writer, but a Callaud cell was used as the constant balancing battery, and the 
measurements were made in terms of this. The Callaltd cell is a gravity battery 
used in telegraphy, and is a modification of Thomson’s gravity battery. As the copper 
is immersed in sulphate of copper, and the zinc in sulphate of zinc, its electromotive 
force is that of a Raoult. The requisite determinations for the purpose having been 
made, the differences of potential are here given in terms of a Raoult. 
The amount and direction of the organ-current in the entire organ were ascertained 
in ten instances ; the fish were killed bv destruction of the brain, but were otherwise 
uninjured. The whole fish was therefore used for experiment, and was fixed with its 
ventral surface against a vertical board ; this was perforated so as to allow the ventral 
surface of the organ to be reached by a leading-off’ electrode. The dorsal and ventral 
surfaces of the organ were now led off by kaolin cushions moistened with '6 per cent, 
saline, and connected with U-shaped non-polarisable electrodes. The points selected 
for leading off were opposite one another on the respective surface, and were situated 
in the middle of the organ. It is surprising, in the light of du Bois-Reymond’s 
statements, what contradictory results were thus obtained, as the following Table 
shows. The difference of potential existing between the dorsal and ventral electrodes 
is indicated in terms of the dorsal electrode. The sign -j-, therefore, signifies that the 
dorsal surface led off is galvanometrically positive to the ventral surface, and that a 
current passes through the organ columns from their ventral to their dorsal ends. 
Small Torpedoes.—-Six animals investigated. 
(Dorsal surface as compared with ventral surface.) 
+ -002 R ; + -001 R ; + ‘0006 R. 
— -0009 R; +-0005 R; +-0015R. 
Medium-sized Torpedoes.—Four animals investigated. 
+ -0017R; — -0011 R; - -0008 R; — ‘0012 R. 
