of the motor impulses in the nerves, he arrived at the idea that these started in the "little spherules" [the neurons] in the cortex of the brain. These little spherules, also called by him with pet-name affection, "little hearts, little brains, little bosoms, most pure and sensitive little wombs," as well as "little factories," he saw as the places in the body where "the spirituous fluid" was perhaps not created but "elaborated" and sent out through the body, not only in the form of nerve impulses, but carried by the blood as that in the blood which was life-giving. He imagined this as a kind of special circulation which he called "the circle of life." 29
Then his synthesizing mind went to work. Having decided that the formation of the embryo was due to a formative force, he identified that with the spirituous fluid, here busy at its first and most important task of forming the body, according to a preconceived image or idea of what was wanted—or else how could organ follow organ in such an orderly and predetermined fashion?
He had, furthermore, found out experimentally that the "faculties" of "understanding, thinking, judging and willing" likewise resided in the "cortical substance," because if it were injured the mind didn't function, so that these faculties too, he concluded, were functions of the spirituous fluid.30
From there it was an easy step to identify the "soul" with the spirituous fluid. He hesitated about terms. Should one not rather say that the spirituous fluid was the "organ of the soul" as the eye was the organ of sight?—"Yet it is no matter whether we call the above fluid itself the spirit or soul, or whether we confine those terms to its faculty of representing the universe to itself, and of having intuition of ends; for the one cannot be conceived, because it is impossible, without the other." 31
Whether Swedenborg called it soul, or spirituous fluid, or animal spirits, or something else, it was still "immaterial." How could it then interact with the demonstrably material cortical substance, "pure and sensitive" as the "little wombs" within it were? What, in his own words, was "the mechanism of the intercourse between the soul and the body"?
Here, where the anatomist failed, the physicist stepped in, even without benefit of quantum mechanics.
