VIII
Often, in contemplating the brain of my patients, pondering over its structure and functions, and seeing the blood coursing through it, I have imagined that I might penetrate into the inner life of the brain-cells, might follow the movements which agitate their minute branches in the labyrinth of the nerve-centres; I have thought I might learn the laws of organic change, the order, harmony, the most perfect concatenations; but my mind might work as it listed, and imagination seize the reins, I never yet saw anything, not the faintest gleam, which gave me hope of penetrating to the source of thought.
During my investigations I have discovered the mechanism with which nature provides for a more rapid circulation of blood when the brain must enter into activity; I was the first to admire some of the phenomena in which the material activity of this organ reveals itself; but although I have scrutinised the functions of the brain with the most exact methods of physiological investigation while it was pulsing under my eyes, while ideas were seething in it, or while it rested in sleep, the nature of the psychic processes still remains a mystery.
We all believe that the faculties of the mind are the fruit of an uninterrupted series of natural causes, of physical and chemical actions which lead from the simplest reflex-movements, step by step, to instinct, reason, sentiment, and will; but as yet nothing has been found which might lead us even to suspect, much less to comprehend, the nature of consciousness.
We attain our firmest convictions in the domain of positivism, not from the narrow field of physiology but from the whole kingdom of science. We imagine that the impressions of the external world form a current which penetrates the nerves, and, without either abatement or check, diffuses and transforms itself in the centres, finally reappearing in the sublime form of the idea; this is the notion of the soul held by the philosophers of remote antiquity; this is the base of modern psychology.
We may suppose that thought must be a form of motion, because the science of the present day demonstrates that all intimately known phenomena may be reduced to a vibration of atoms and to a displacement of molecules.
I can think of my brain by the analogy which it must have with that of another; but the bridge which leads me from external to internal observations I cannot find; between physical and psychic phenomena there is a gulf which we cannot pass.
The soul was regarded by the ancients as a harmony. But how this sublime harmony of imagination, of memory, of the passions, and of thought, results from the vibration of the molecules constituting the brain, no one knows. The road which connects psychic facts with the transformation of energy has not yet been pointed out.
I know the chemical transformations which give rise to the mechanical work of the muscles of my hand in writing, but I do not know the processes of my brain which thinks and dictates.