3 Fundamentals of the Formation of Biosignals

This chapter introduces the history and the interesting topic and the concepts of the

formation of biosignals. Following the historical explanations in [47, 71, 86], the dis-

covery of bioelectric phenomena reaches back to the year 2750 B.C., where at first bio-

electrical activity was observed in the accidental and painful contact with electric fish.

Besides the catfish, which generates voltages on the order of 350 volts, the electric

ray¹ is also known for this characteristic. The latter, despite considerable potentials

between 60 and 230 volts, was used for medical treatments as early as the 1st century

AD.

The mode of action became clearer in the 18th century, based on the work about

electricity by the physicist Georg Christof Lichtenberg², the Briton John Walsh was

the first to make the discharge of the organ visible by a flash of light during his in-

vestigations [80]. At about the same time, the Italian physician and anatomist Luigi

Galvani³ discovered by chance the contraction of prepared frog legs when they came

into contact with a bimetallic strip of copper and iron [5] . These findings raised the

fundamental question of the significance of electricity for living organisms – it was

even regarded in those days as the central distinguishing feature between animate

and inanimate matter.

According to the historical records in [5, 12], Luigi Galvani and the physicist Aless-

andro Volta⁴, who at the time were studying the phenomena of electricity, also con-

sidered electricity to be the basis of the activity of the nerve and muscle cells of living

beings. Galvani himself called the phenomenon "animal electricity" based on his find-

ings about the electrical activity of fish and claimed to have discovered a new form of

electricity in his experiment. He assumed that animal electrical energy present in the

tissue was discharged by contact with the metals and that this triggered the contrac-

tion of the muscle. Volta, on the other hand, assumed that there was only one form

of electrical energy and claimed that the movements caused by contact with the two

metals were due to an electrostatic potential difference between the metals, which was

transferred to the animal’s muscle. To argue against independent animal electricity,

he presented the voltaic pile⁵ as a model of an electrical organ, thus he demonstrated

the similarity to the natural electrical organ of the electric ray [12]. Even if Volta was

1 Torpedinidae from Lat. torpere = to be paralysed.

2 Georg Chr. Lichtenberg (1742–1799), German physicist and one of the co-founders of the theory of

electricity; he became known for the Lichtenberg-figures named after him.

3 Luigi Galvani (1737–1798), Italian physician, physicist, biologist and philosopher, was considered a

pioneer of bioelectromagnetics.

4 Alessandro G. A. A. Earl of Volta (1745–1827), Italian physicist, inventor of the battery and co-founder

of the theory of electricity.

5 The voltaic pile consisted of thin zinc and copper discs separated by cardboard discs soaked in

saline solution.

https://doi.org/10.1515/9783110736298-003