OF THE ELECTRICAL ORGAN OF TORPEDO MARMORATA. 
535 
Conclusion. 
The work done at Arcachon has thus brought out the different excitatory changes 
which are produced by different methods of excitation in the organ. 
The electrical organ of the Torpedo responds to a stimulus by a change in the 
electromotive character of the elements which make up its hexagonal columns. 
These elements are plates composed of nucleated protoplasmic masses and nerve- 
fibres. An extraordinary number of these are present in, and as it were bound 
together by, the former. In the active state of the organ the ventral surface of each 
plate with its contained nerves becomes negative to the dorsal surface; the effect in 
all the plates of a column when summed np is, therefore, such that the dorsal end of 
the column becomes positive to the ventral end. This effect may be produced in at 
least three different ways, and in each case it presents features which are those of the 
excitatory process. 
i. The obvious method of production is that of excitation of the trunk of the 
electrical nerve. The nerve-organ response is characterised by a short period of 
delay, an extremely rapid development, occupying less than and a less rapid 
decline. If the response is very pronounced, the main effect lasts yfo", but is followed 
by a prolonged after-effect in the same direction. 
ii. This after-effect is itself an excitatory change, and may be produced by the 
passage of a sufficiently intense current of short duration through the organ. This 
excitatory change is probably developed more or less rapidly, but is especially 
characterised by its slow subsidence, as it does not entirely disappear until several 
minutes after its production. 
iii. A more prolonged electromotive change of the same character is produced when 
by mechanical or thermal means a large number of electromotive elements are injured. 
The adjacent parts are then thrown into a state of prolonged excitation, the effect 
taking some hours to subside. 
Whilst then response i. is an affair of fractions of seconds, ii. is an affair of 
fractions of minutes, and iii. of fractions of hours. All three effects are characterised 
by positivity of the dorsal aspect of the column, and thus of the plates; and in all 
three the decline occurs at first rapidly and then more slowly. 
The production of these three conditions not only brings the Torpedo organ into 
analogy with other electromotive tissues, muscle, nerve, &c., but throws some light 
upon the phenomena displayed by the latter tissues. It is the special characteristic 
of the electrical organ that any excitatory change must always, whether local or 
general, produce electromotive phenomena of the same kind ; the dorsal surface of the 
columns must become positive to the ventral. 
In the organ of the Torpedo it is easj T to recognise the fact that in the effect of 
injury which corresponds to the demarcation-current we are dealing with a state 
of excitation. This is not so easilv recognised in such tissues as muscle and nerve, 
%J o * 
