Page:Life in Motion.djvu/207

Rh either gills (organs for breathing) or feet (organs for locomotion). We might expect, then, that electrical organs might be found that were not muscular in their origin.

Accordingly we find that the electrical organ of the raasch or thunderer fish of the Arabs (Malapterurus electricus), an inhabitant of the Nile, is not muscular, but is a modification of peculiar glandular structures found below the skin of allied species.

Electrical organs, in their physiological behaviour, present many striking resemblances to muscle. Thus they are all richly supplied with nerves. When the nerve is irritated the electrical organ discharges electricity, not as a current, but in a number of short sudden shocks, like the quivers of a muscle in tetanus. The battery, however, does not go off at once. There is a latent period preceding the discharge. The electrical organ is connected