10. ELECTRIC ORGANS
357
give the equivalent of differential recording. However, differential
recordings often are more easily interpreted and electronic subtraction
is much easier than the same process done graphically. An additional
advantage is that interfering potentials resulting from activity of distant
cells tend to be about the same size at different monopolar electrodes and
are thus subtracted out by differential recording.
It is useful and often essential to pass stimulating currents through
the faces. When current is passed from an intracellular electrode to an
indifferent electrode, it flows outward through both faces in amounts
depending on their resistances, capacities, and any responsiveness they
exhibit as well as on the external resistances. Each face is depolarized
and a response of one face may obscure a response of the other. For this
reason it may be desirable to pass current between an external electrode
outside one face and the indifferent electrode. (Use of two external electrodes, one outside each face, would be preferable in some ways but has
not been carried out because of added technical complexity.) In this case
part of the applied current flows inward through one face and outward
through the other. Since this current polarizes the faces in opposite
directions, it is generally simpler to evaluate the responsiveness of the
two faces.
Electrocytes have been studied both in situ and in isolated tissue
bathed in suitable physiological saline. For in situ work normal organ
discharge can in many species be stopped by spinal section. Curare
which blocks vertebrate neuromuscular transmission also blocks nerveelectrocyte transmission. It can be used to immobilize a fish as well as
to block neurally controlled activity of myogenic electrocytes, but of
course it prevents study of nerve-electrocyte transmission.
In a number of instances it is possible to apply currents to columns of
cells or even to part of the intact animal. By means of a bridge circuit
the potential resulting from voltage drops across fixed resistances in
series with the active tissue can be subtracted from the records, and
information similar to ( and supplemental of) that obtained from single
cells can be obtained ( Albe-Fessard, 1950b; Bennett, 1961; Bennett et al.,
1961). The success of experiments of this kind is dependent on the series
arrangement of the active membranes.
B. Membrane Properties
The surface membranes of electrocytes exhibit a number of different
passive and active properties. In considering these properties, it is convenient to think of the cell surface as containing various kinds of sites
357
give the equivalent of differential recording. However, differential
recordings often are more easily interpreted and electronic subtraction
is much easier than the same process done graphically. An additional
advantage is that interfering potentials resulting from activity of distant
cells tend to be about the same size at different monopolar electrodes and
are thus subtracted out by differential recording.
It is useful and often essential to pass stimulating currents through
the faces. When current is passed from an intracellular electrode to an
indifferent electrode, it flows outward through both faces in amounts
depending on their resistances, capacities, and any responsiveness they
exhibit as well as on the external resistances. Each face is depolarized
and a response of one face may obscure a response of the other. For this
reason it may be desirable to pass current between an external electrode
outside one face and the indifferent electrode. (Use of two external electrodes, one outside each face, would be preferable in some ways but has
not been carried out because of added technical complexity.) In this case
part of the applied current flows inward through one face and outward
through the other. Since this current polarizes the faces in opposite
directions, it is generally simpler to evaluate the responsiveness of the
two faces.
Electrocytes have been studied both in situ and in isolated tissue
bathed in suitable physiological saline. For in situ work normal organ
discharge can in many species be stopped by spinal section. Curare
which blocks vertebrate neuromuscular transmission also blocks nerveelectrocyte transmission. It can be used to immobilize a fish as well as
to block neurally controlled activity of myogenic electrocytes, but of
course it prevents study of nerve-electrocyte transmission.
In a number of instances it is possible to apply currents to columns of
cells or even to part of the intact animal. By means of a bridge circuit
the potential resulting from voltage drops across fixed resistances in
series with the active tissue can be subtracted from the records, and
information similar to ( and supplemental of) that obtained from single
cells can be obtained ( Albe-Fessard, 1950b; Bennett, 1961; Bennett et al.,
1961). The success of experiments of this kind is dependent on the series
arrangement of the active membranes.
B. Membrane Properties
The surface membranes of electrocytes exhibit a number of different
passive and active properties. In considering these properties, it is convenient to think of the cell surface as containing various kinds of sites