What did Descartes envision as a function of the brain and nervous system?

Descartes envisioned nerves as hollow tubes that functioned as channels for animal spirits, which he believed were a form of fluid flowing through these structures. This idea was part of his dualistic view of the mind-body relationship, where he perceived the body as a machine that operated through physical processes. The notion of nerves as hollow tubes allowed him to propose that sensory information and motor commands could travel through these passages, much like a hydraulic system. This conceptualization laid the groundwork for later scientific advancements in understanding the nervous system, even though modern biology has since provided a different and more complex view of neurological function.