How Swedenborg was able to come to this modern conception ought not to be so exceedingly difficult to understand if we summarize what was already known at that time about these cortical elements and add thereto the conclusions as to the functions of the cortex to which Swedenborg had already come.
In Swedenborg’s time the conception of Hippocrates of the brain as a gland was still generally received. In this one had, however, as Malpighi says, ›since the time of Piccolomineus› learned to distinguish between an outer, greyish layer, ›cerebral cortex›, and an inner, more pure white mass, the ›cerebral medulla›.[81]
Through the microscopic investigations of Leeuwenhoek (1632-1723) it had further been discovered that the substance of the brain (especially of the cortex) contained, besides a great mass of blood-vessels and very fine fibres, a numberless mass of peculiar small bodies of varying size, by him called ›globuli›, connected with the vessels and fibres. (See Œc. R. A. II., Nos. 71-75, 112, etc.).
Malpighi, (1628-1694), had closely examined these ›globuli› and described them as small oval or polygonal ›glands›, which were closely surrounded by blood-vessels, and in their inner central ends sent forth processes forming vessel-like fibres which continued into the cerebral medulla.[82]
As these fibres or vessels formed small clusters, the little glands hanging on their extreme ends, like ›dates on their stems›, as Malpighi expresses it, thus formed small groups.
Within these groups the cortical elements were, however, well isolated from each other by clefts, which indeed sometimes were very small, but could nevertheless be plainly demonstrated with the aid of colouring matter.[83]
The cortical elements taken together formed the winding groups which on the surface of the brain gave rise to the so called gyres.[84]
The profusion of blood-vessels, as was said, Leeuwenhoek and Malpighi had already described as being very great, but Ruysch (1638-1731) had afterwards by his famous vascular injections found it to be so great that he would not call the cortex a glandular but actually a ›vascular› tissue. (Œc. R. A., II., No. 86). Because of the enormous wealth of blood-vessels there was thus carried to the cortical substance, especially to the little follicles, a plenteous quantity of blood, and from this, according to the opinion of that day, the most subtile components of the blood could pass to the cortical elements and thereby be transformed into ›spiritus animalis›. And finally, the Italians Bellini, (1643-1704), and Zambeccari had shown by their analyses that the juice of the brain possessed a highly subtile composition, above all a great volatility and lightness, and was exceedingly mobile. (See Œc. R. A. II., Nos. 88, 96, 119). All this Swedenborg has himself quoted in his works.
On the basis of these and some other anatomical and physiological data, in conjunction with a number of clinical and experimental observations, Swedenborg, as we have before seen, came to the conclusion that it is in the cortex that the soul’s activity comes into being; but at the same time he concluded that, strictly speaking, the cortical elements were the real work-shops. For he reasoned in the following manner: When the sensory impressions enter the brain, they certainly proceed no further than to the ›Sphaerulae› of the cortex, since these constitute the beginnings of the nerve and medullary fibres: were they to go further, for instance to the small arteries which surround the cortical elements, or to the membranes of the brain, then they would overstep the boundary, as he says, and leave the actual centre and go out to the more peripheral parts.[85]