As is well known the general principles of the macroscopical anatomy of the brain were known long before SWEDENBORG’s days; and even its microscopical structure had, half a century before his time, begun to be studied by such men as LEEUWENHOEK (1632-1723), MALPHIGI (1628-1694), and others. For example, it was not only known that the substance of the brain, upon incision, exhibits an outer, greyish layer, the cortex, and an inner, more pure white mass, the medullary substance; but the above-mentioned investigators had also shown that _the cortex of the brain_ consists of a numberless mass of small globular bodies, which are closely surrounded by blood-vessels and are continued in small thread-like extensions, which run into the medullary substance.[28] Now SWEDENBORG succeeded, as regards _these globular bodies_, in arriving at the conception that they are _the most important components of the cortex_ and that it is in these bodies that the nerves originate.[29] He called them ›_Sphaerulae_› or ›_Cerebellula_›. Again, as regards the _medullary substance_, it was already known through the works of WILLIS (1622-1675), VIEUSSENS (1641-1716), BOERHAAVE (1668-1738), that it consists, for the most part, of a great mass of finer and coarser nerve-fibres, and that these, through the medulla oblongata,[30] continue down into the spinal cord, and that through the nerves they are in communication with the various parts of the body. The nerves were supposed to contain a lumen, thus being tubular. On the basis of certain _clinical experiences_ concerning the changes which occur in the functions of the soul, when the cortex of the brain is injured, SWEDENBORG succeeded in drawing the conclusion that the _same_ medullary fibres which are derived from the ›Cerebellula› of the cortex of the brain, continue into the spinal cord and are in connection with the nerves, and that thus an easily transmitted and continuous communication is established between the substance of the cerebral cortex and all the parts of the body, where the nerves are distributed.[31] Concerning the _function_ of the brain, the old view of HIPPOCRATES that the brain was a gland was still entertained in SWEDENBORG’s time. The cortical substance served for secreting the ›spiritus animalis›, that is, what the ancients called the ›spirits of life›, and these were collected in the cortex of the brain that they might, when necessary, stream out through the nerves. The medullary substance was, according to the latest conceptions of that day, the origin and source of the soul’s activity, and the ›spiritus animalis› served as the connecting link between the soul and the sense-organs and muscles of the body.