Bioelectric Currents

BIOELECTRIC CURRENTS, currents that arise under certain conditions in a plant or animal organism (for details see Animal electricity). Electrical phenomena discovered in the bodies of animals and plants when individual parts of the organisms are connected to sensitive galvanometers are called bioelectricity or animal electricity. These phenomena were first discovered by Galvani, who observed cases of contraction in a frog preparation when a muscle current was closed through a nerve; in this case, the muscle connected to the nerve contracted. Further progress is represented by the works of Matteucci and, especially, the profound classical studies of Du Bois-Reymond on animal electricity. These latter works, which created a new methodology (non-polarizable electrodes, multipliers, the method of measuring potential difference, etc.), have not lost their interest to this day. They also established the fundamental facts of bioelectricity: if an electric current is led off from an excited and an unexcited site of a living organ, one can observe that the excited part of the organ is always electronegative in relation to the unexcited site, which is electropositive (action currents). Currents can also be observed during the rest of the organ. The explanations that are currently acceptable for bioelectric currents are as follows. One can expect that during excitation phenomena, an accumulation of ions occurs, which act in an excitatory manner on tissues (see Ions and Excitation). The accumulated ions thus alter the potential difference between the excited part and the unexcited part and give rise to phenomena that correspond to bioelectric currents. Detailed study of the nerves of sense organs, as well as the central nervous system, has shown that similar electrical phenomena are always observed upon excitation. It can be shown that in the central nervous system, in the absence of external stimulation, when observing currents with the help of a telephone, one can obtain characteristic noises depending on periodic spontaneous discharges occurring in the central nervous system. Finally, it has recently been possible to show that analogous currents appear in the bodies of plants, and there are many analogies between the phenomena of bioelectricity in animal and plant organisms. Electrical phenomena in the bodies of electric fish (electric ray) also pertain to bioelectricity.