BOERHAAVE, for instance, says, in his ›Institutiones medicæ›, when speaking of the sensations, that they give rise to _different perceptions_, partly owing to the differing species and nature of the outer objects, and partly to the different natures of the sense-organ and the affected nerve, but partly also _to the different regions in the cerebral medulla from which the nerve proceeds_. Thus we have here a kind of localization to a special region of the brain, although in its _medulla_.[71] And still more clearly does BOERHAAVE express the same idea in his ›Prælectiones academicae,› where he says: ›In the ’Sensorium commune’ there are _regions locally distinguished for the different senses, just as every sense has its own special sense-organ_.›[72] And before BOERHAAVE the philosopher DESCARTES had expressed an idea concerning a certain form of localization of the various elements of psychic activity. For he supposed that the images of sensation and the images of the memory, etc., which the soul perceives, arise on those places on the walls of the brain’s central ventricle, where, according to his opinion, the various nerves originate. In a similar way he also imagined the origin of motility localized. (R. DESCARTES: ›De homine›, publ. by F. SCHUYL, Ludg. Bat., 1662). 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). [Illustration: 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.