The fish died soon after this, but replacements were acquired, and working with his exceptionally capable research assistant Kenneth E Machin (1924-1988), whose PhD had covered radio-astronomy, Lissmann was able, through observation and measurement, to demonstrate that the variable electrical charge was produced by the knife fish itself, and that the fish reacted to any change in the electric field around it, even when produced close to, but outside, the fish tank itself. They were helped in their work by a perspex model of an African knife fish constructed by Ken Machin, with two electrodes attached to it permitting the perspex fish to generate an electric field equivalent to that produced by the real fish.
Following the demise of the fish, replacements were sourced, and with the assistance of his exceptionally skilled research collaborator Kenneth E Machin (1924-1988), whose doctoral work centered on radio-astronomy, Lissmann was able to demonstrate through observation and measurement that the electrical charge fluctuations were produced by the knife fish itself, and that the fish reacted to any changes in the electric field surrounding it, even when generated outside the tank.