We have learned a good deal about the special significance of the various parts of the brain, as organs of specific functions, by the progress of the modern science of experimental physiology. Careful experiments by Goltz, Munk, Bernard, and many other physiologists, have shown that the normal consciousness, speech, and the internal sense-perceptions, are connected with definite areas of the cortex, and that these various _parts of the soul_ are destroyed when the organic areas connected with them are injured. But in this respect Nature has unconsciously given us the most instructive experiments. Diseases in these various areas show how their functions are partially or totally extinguished when the cerebral cells that compose them (the _neurona_ or ganglionic cells) are partially or entirely destroyed. Here again Virchow, who was the first to make a careful microscopic study of the finest changes in the diseased cells, and so explain the nature of the disease, did pioneer work. I still remember very well a spectacle of this kind (in the summer of 1855, at Würzburg), which made a deep impression on me. Virchow's sharp eye had detected a small suspicious spot in the cerebrum of a lunatic, though there seemed to be nothing remarkable about it on superficial examination. He handed it to me for microscopic examination, and I found that a large number of the ganglionic cells were affected, partly by fatty degeneration and partly by calcification. The luminous remarks that my great teacher made on these and similar finds in other cases of mental disorder, confirmed my conviction of the unity of the human organism and the inseparable connection of mind and body, which he himself at that time expressly shared. When he abandoned this Monistic conception of the psychic life for Dualism and Mysticism twenty years afterwards (especially after his Munich speech in 1877), we must attribute this partly to his psychological metamorphosis, and partly to the political motives of which I spoke in the last chapter. We find another series of strong arguments in favour of our Monistic psychology in the individual development of the soul in the child and the young animal. We know that the new-born child has as yet no consciousness, no intelligence, no independent judgment and thought. We follow the gradual development of these higher faculties step by step in the first years of life, in strict proportion to the anatomical development of the cortex with which they are bound up. The inquiries into the child-soul which Wilhelm Preyer began in Jena twenty-five years ago, his careful "observations of the mental development of man in his early years," and the supplementary research of several more recent physiologists, have shown, from the ontogenetic side, that the soul is not a special immaterial entity, but the sum-total of a number of connected functions of the brain. When the brain dies, the soul comes to an end.