OF THE ELECTRICAL ORGAN OF TORPEDO MARMORATA. 
503 
owing to the lack of suitable methods; they only showed that the decline was more 
rapid when the organ was excited. 
The facts relating to the organ-current may now be summed up as follows :— 
The difference between the dorsal and ventral surface of the organ is very small in 
the uninjured organ when examined in situ, and under these circumstances is often 
of opposite sign in different animals. 
When a portion of cut tissue is examined an electromotive difference is always 
found to be present, and is such that the dorsal surface of the columns is positive to 
the ventral. 
This difference subsides at first rapidly, and then so slowly that it may be observed 
one or two hours after the preparation has been made. 
The difference is produced by incisions which cut through the columns in the 
direction of their length, thus cutting the electromotive elements at right angles to 
their length. 
The most effective method for its production is the thermal section of the external 
columns contained in a strip of the tissue. 
The amount and not the direction of the effect is affected by partial injury of 
a column, whether this be dorsal or ventral. 
The organ-current is thus analogous to the demarcation-current of muscle and 
nerve, and is believed to correspond to a prolonged local excitation of the vital 
electromotive elements in the immediate neighbourhood of the injury. 
II. Experiments relating to the Time Relations of the Excitatory Change in the 
Organ following Excitation of its Nerve. 
The method used in these experiments was that rendered familiar by its employ¬ 
ment in experiments of a similar kind upon other tissues, particularly cardiac tissue. 
This consists in the use of a rheotome w T hich shall connect the galvanometer with the 
tissue under investigation during a known period after excitation of the tissue. In 
the experiments of Marey upon the Torpedo (24) a fast-travelling plate, such as that 
of the pendulum or spring myograph of du Bois-Reymond, was used. The movement 
of the plate was arranged to ensure both the passage of an induction shock at a given 
point in its course and a definite closure (for joWc/) °f the circuit which connected 
the organ of the Torpedo with the “ physiological galvanoscope,” this being the nerve 
muscle preparation of the frog—the movements of which were recorded on the travelling 
plate. This method had been used by myself in ascertaining the time relations of the 
response of the Malapterurus to excitation of its skin (25). The information which 
this method gives is, however, of relatively little value, since it is obtained in terms 
which bear no sort of relation to those applicable to electrical phenomena in general, 
such as the deflections of a galvanometer needle of known sensibility, &c. To obtain 
such information as this latter was the object of the following experiments. 
