From Chapter 6 – The Battle of the Frogs
Italian scientist Luigi Galvani was a professor of anatomy at Bologna. In 1780 he had begun a series of experiments with his students aimed at illuminating the nervous system through the dissection of frogs. Also in the laboratory they were working in was an electrical machine, a friction generator, which Galvani was using in other research. The frogs were pinned out on dissecting boards one day as usual when a student noticed something curious:
It happened by chance that one of my assistants touched the inner crural nerve of the frog, with the point of a scalpel; whereupon at once the muscles of the limbs were violently convulsed. Another of those who used to help me in electrical experiments thought he had noticed that at this instant a spark was drawn from the conductor of the machine. I myself was at the time occupied with a totally different matter; but when he drew my attention to this, I greatly desired to try it for myself, and discover its hidden principle. So I, too, touched one or other of the crural nerves with the point of the scalpel, at the same time that one of those present drew a spark; and the same phenomenon was repeated exactly as before.
Galvani’s curiosity was roused. He had noticed two things, the first of which was that the twitching happened at those times when the electrostatic machine was sparking. Further investigation revealed another curious effect – it only happened when the bone-handled scalpel was used in such a way that the student was touching the metal blade at the time. Galvani investigated further. He substituted a glass rod for the scalpel blade and repeated the experiment but nothing happened; however, when he substituted an iron rod for the scalpel the twitching recommenced, providing the machine was sparking. Galvani concluded that the frogs’ legs were twitching in response to direct electrical stimulus and he wondered if this might be due to atmospheric electricity being produced by the machine.
Taking things a little further, the scientist proceeded to festoon the garden of his home with a gruesome display. Possibly inspired by Benjamin Franklin’s experiments flying kites during thunderstorms, he took an array of frogs, each with a brass hook through its spinal cord, and hung them from the iron railing around his garden and then waited to see what happened. Galvani found that the legs did twitch, but he also noticed that the twitching stayed the same whether there was lightning in the air or not. It was also less violent than it had been in the laboratory. Becoming impatient with the lack of expected results, Galvani lent a hand and began to press the hooks in the spinal cords against the railing to see what would happen. Sure enough, there were contractions, and again it mattered not whether the skies were clear or thundery. This led Galvani to the almost inevitable conclusion that his initial hypothesis about atmospheric electricity was wrong. However, he still believed there was an important discovery waiting to be made and that his frogs held the key.
Galvani took down the grisly totems in his garden and went back to work in his laboratory. Remembering that the only significant results he had obtained in his outdoor experiment had come when he pressed the hooks against the railings, he replicated these conditions in the lab. He laid the newly dissected frogs out on an iron plate and found that when he pressed each hook against the plate he got a noticeable contraction in the attached frog’s legs. As he had done with the scalpel, he experimented with various combinations of metals. He found, for example, that an iron hook touched to an iron plate produced no effect at all and reasoned that two different types of metal had to be used. After experimenting with various combinations he discovered that zinc and brass seemed to produce the most dramatic results. One thing was missing in these experiments that had been present when the phenomenon was first observed – this time there was no electrical apparatus sparking in the room. It was the presence of this machine that had led Galvani to believe that the frogs were detecting and reacting to electricity in the atmosphere. Now there was no electricity in the room but the legs were still twitching. For Galvani there was only one possible conclusion – if the electricity was not in the room then it must be in the frog. This naturally occurring ‘animal electricity’, as his concept came to be known, was providing the stimulus to provoke the twitching. If it could do that, thought Galvani, perhaps it might even be the key to life.
In 1791 Galvani published his conclusions in a landmark work entitled De viribus electricitatis in motu musculari commentarius ‘Commentary on the Effects of Electricity on Muscular Motion’. They took the scientific community by storm and provoked a wave of debate. Had this unfashionable scientist from Bologna really discovered the secret of life? If Galvani’s theories were correct they would have profound implications for theology, medicine and many other areas of life. How,
for example, did this animal electricity sit with the concept of the soul? If the soul were downgraded from its position as our animating force then what of the influence of the Church? Medically it had been felt that the heart was the repository of life, but this notion of animal electricity suggested the brain might be more important.
View cart
