We here reproduce some illustrations from the work of Descartes just mentioned, which are designed to show how he thought that the images of sensation arise. — — See the figures 1, 2, 3.
We thus see that the idea of localization itself was not altogether new. But how did Swedenborg ultimate and develope it?
With regard to function Swedenborg divided the hemispheres of the cerebrum into two parts: one anterior region and one posterior, conceiving the fissure of Sylvius as the dividing boundary between them. (›The Brain›, Nos. 16, 88, 91).
Transcriber’s Note: Click for larger version.
Fig. 1. Fig. 2. Fig. 3. Fig. 4.
Figures 1-3. Reproduced from Descartes: ›Tractatus de homine›.
Fig. 1. A part of the wall of the central ventricle of the brain. The points of the dotted area represent the openings of the nerves, which, according to the opinion of Descartes, take their origin in the wall of the ventricle. The figures O (star) and B (lily) are formed by combinations of such nerve openings.
Fig. 2. View of the left hemisphere from the medial side. The dotted area B represents the place, where, according to Descartes, the nerves originate. The vesicle H is the pineal gland, wherein the soul was thought to have its seat.
Fig. 3. Illustrates the act of seeing. The object ABCD forms an image, 1357, on the retina of the eye. This image provokes a similar image, 2468, on the wall of the brain’s ventricle, by exciting a stream of ›spiritus animalis› from the central ventricle through certain of the fine nerve tubules of the optic nerve, the openings of the nerve tubules in the wall of the ventricle being widened and thus forming images (of sight), which the soul is able to perceive from its seat in the pineal gland.