Electricity in the body: Luigi Galvani
Luigi Galvani (1737- 1798)
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Luigi Galvani was an Italian physician and biologist, and is known for his work on bioelectricity, and for laying the foundations of electrophysiology- the branch of science focusing on electricity in the body. He was born in 1737 in Bologna, Italy, and died in 1798 when the age of electricity was approaching. Galvani began his career as a doctor after he graduated with a thesis in 1762, at the University of Bologna. The same year, he became a Reader in Anatomy at the university. He was then given the Chair of Obstetrics at the Institute of Sciences, owing to his surgical skills, and became its president in 1772. He held his chair for 33 years but was dismissed in 1797 when Napoleon’s army invaded but was reinstated sometime later.
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Galvani's discovery
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Galvani was performing experiments on frog legs at the University of Bologna, when his assistant touched his scalpel to the crural nerves of the frog, when he was drawing spark from the brass conductor of the electrostatic machine, and the frog leg twitched. Due to the current, muscular spasms were generated throughout the body. Galvani was intrigued and performed more experiments to see if he would get the same result. He did- the experiment was reproducible. Galvani used a Leyden jar (a device which stores static electricity, an early form of capacitor), and an electrostatic machine to produce this electricity. He knew that metals transmitted something called electricity, and a form of this electricity was presumably generated in the frog tissue to allow muscular contraction- he named this ‘animal electricity’. He believed this ‘animal electricity’ was different from static, and natural electricity e.g. lightning. Indeed, in 1786, during a lightning storm, he touched some frog nerves with a pair of scissors and the muscle contracted. Galvani thought ‘animal electricity’ as a fluid secreted by the brain, which flows though nerves and activates the muscles. This is how his experiments helped pave the way for electrophysiology in neuroscience.
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In 1786, during a lightning storm, Galvani touched some frog nerves with a pair of scissors and the muscle contracted.
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Galvani's experimental setup consisted of frog legs, a Leyden jar, and an electrostatic machine.
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He knew that metals transmitted something called electricity, and a form of this electricity was presumably generated in the frog tissue to allow muscular contraction- he named this ‘animal electricity’. A first step in the branch of electrophysiology.
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Galvani's progress in the field
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Galvani’s work was accepted by all his colleagues except for Volta, the professor of physics at the University of Pavia. Though Volta could reproduce Galvani’s experiments, he did not like Galvani’s explanation of ‘animal electricity’. Volta believed it was the two dissimilar metals producing the electricity, he named it ‘metallic electricity’, and there was no current running inside the frogs- there was no ‘animal electricity’. Galvani argued that there were electric forces inside organisms, and in 1794 he published an anonymous book Dell’uso e dell’attivita dell’arco conduttore nella contrazione dei muscoli (“On the Use and Activity of the Conductive Arch in the Contraction of Muscles”), where Galvani described his work on how he obtained electricity inside the frog, without the use of any metal. It was reported that he did this by touching the exposed muscle of one frog with a nerve of another, and the muscle contracted (Dibner 2020). This seems doubtful as Galvani’s forceps must have been in contact with spark for there to be movement. Still, it was the first attempt to demonstrate the existence of bioelectric forces.
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Outside of neuroscience
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The term ‘animal fluid’ Galvani used, is reminiscent of ‘animal spirits’, which was used by Rene Descartes, French philosopher, in the 1600s. Descartes described ‘animal spirits’ as a fluid flowing through the brain and the body, and Galvani unwittingly built on this belief with his findings on bioelectricity; the spirits ‘became’ “electricity”. There was a paradigm shift as Descartes thought that nerves were water pipes, but they were electrical conductors. This illustrates how Galvani was able to build on existing ideas in science.
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Limitations
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Even with the vigorous experiments and support, there was one limitation. For a direct correlation between frog muscle contraction and electricity generation, Galvani needed to be able to quantitatively measure the electrical currents generated in the muscle. This was difficult to do at the time since there was not enough technology to measure the currents- the currents were too small. Eventually, in the early 1900s when there were major advances in technology, Muller, Bois-Reymond, and Helmholtz, three German physiologists, managed to successfully measure the conduction of electrical activity along the nerve axon. This breakthrough furthered the branch of electrophysiology which Galvani had started.
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Summary
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In conclusion, Luigi Galvani was an influential physician and biologist, who founded the branch of electrophysiology with his experiments on frogs and metals. His results were crucial to the development of neuroscience, particularly the beginning of understanding electrical activity along the axon.
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By Manisha Halkhoree
