Just as the purpose of the brain and the heart confused ancient scientists, so did the nervous system. Nerves had been identified fairly early but they proved difficult to categorize. Some thought it was similar to arteries and formed some sort of connective system for tissues. In fact, the word nerve is Greek for tendon or sinew, suggesting that it was thought to be some sort of physical connection.
Despite the confusion about its exact mechanism, ancient medical practitioners seemed to understand its function. Nerves were attributed to both movement and sensation correctly, even though there were opposing views on what controlled these functions. Aristotle argued that nerves originated and were controlled by the heart, while others argued nerves were controlled by the brain. Centuries later, Galen proved that nerves emanated from the brain, scoffing at those “who know nothing of what is to be seen in dissection."
Galen was the first to conclude that the spinal cord was an extension of the brain and carried sensation to the limbs, and nerves controlled the actions of muscles in the limbs. He attributed the nerves controlling sensation to soft nerves and motion to hard nerves. Another description about nerves was also wrong- the structure of nerves was thought to be hollow tubes. Galen theorized that the hollow nerves carried the animal spiritus, the body's principal source of vitality allowing it to circulate throughout the body. Different anatomists came up with different theories of how the nerves created emotions and sensations in different parts of the body by attaching and carrying the spiritus to different organs.
Despite the confusion about its exact mechanism, ancient medical practitioners seemed to understand its function. Nerves were attributed to both movement and sensation correctly, even though there were opposing views on what controlled these functions. Aristotle argued that nerves originated and were controlled by the heart, while others argued nerves were controlled by the brain. Centuries later, Galen proved that nerves emanated from the brain, scoffing at those “who know nothing of what is to be seen in dissection."
Galen was the first to conclude that the spinal cord was an extension of the brain and carried sensation to the limbs, and nerves controlled the actions of muscles in the limbs. He attributed the nerves controlling sensation to soft nerves and motion to hard nerves. Another description about nerves was also wrong- the structure of nerves was thought to be hollow tubes. Galen theorized that the hollow nerves carried the animal spiritus, the body's principal source of vitality allowing it to circulate throughout the body. Different anatomists came up with different theories of how the nerves created emotions and sensations in different parts of the body by attaching and carrying the spiritus to different organs.
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| Leonardo da Vinci's drawing of the brain with cranial nerves as hollow tubes |
Because of this theory that prevailed much through history,
the exact mechanism by which nerves controlled movement and sensation remained
a mystery until much later. Only in the late 18th century,
scientists began to consider electricity as the mechanism governing the nervous
system, and new theories about the nervous system came into consideration.
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