Pathology and psychiatry with their vast stores of facts go to confirm the psycho-physiological hypothesis. In general paralysis, for instance, we meet conditions somewhat similar to those of alcoholic intoxication. At first inhibitions are removed, the psychomotor processes become deranged and slightly stimulated, sooner or later to be followed by gradual paralysis. The process of dissolution progresses from the highest most complex, least stable functions, memory, intelligence, will and so on, to the lower, less complex and more stable functions, reading, writing, playing, etc., finally reaching to the very lowest, to the simplest co-ordination of movements, mastication, swallowing, etc. A post-mortem examination of the brain uniformly reveals a profound degeneration of the brain cells. In the various forms of epilepsy and in most cases of chronic insanity, ending in dementia, we find on examination as a rule, some degeneration of the brain cells.
In cases of the many forms of aphasia, science triumphed in discovering the brain lesion. In motor aphasia the third frontal convolution, or that of Broca is found to be degenerated, in sensory aphasia the degeneration is in the first temporo-sphenoidal convolution, or that of Wernicke. In many other nervous diseases where there is a profound change in the sensori-motor functions, such as posterior spinal sclerosis or locomotor ataxia, acute ascending paralysis, acute poleomyelitis anterior, syringomyelia, etc., we also find degeneration in some one part of the cerebro-spinal nervous system. Thus in tabes we find a degeneration of the posterior root zones often associated with similar lesions in the intramedullory continuation of the several cranial nerves. In poliomyelitis anterior we find an inflammation of the anterior cornua (sometimes extending in the antero-lateral columns); the multipolar cells with their dendrons and neuraxons are destroyed. In syringo-myelia we find the formation of one or more cavities within the substance of the spinal cord, usually within the horns of the gray matter the cavities being filled with a fluid which is either liquid or gelatinous. We find in these diseases definite organic changes concomitant with definite sensori-motor modifications.
In the functional diseases belonging to the province of psycho-pathology, diseases such as are known under the vague term of hysteria in all its protean manifestations, the different forms of anaesthesia and amnesia, abulia, psychopathic chorea, astasia-abasia and numerous others, where no organic lesion in the cerebro-spinal nervous system can possibly be discovered, we have good reasons for suspecting some functional derangement into the psysiological processes of the nervous system. My own psycho physiological investigations in this line tend strongly to confirm the theory that all functional diseases are disassociations of functioning brain cell-systems, and that the gravity of the disease depends on the extension of such functional dissociations. Thus we find that neuro-pathology and the recent science of psycho-pathology with all the wealth of facts and discoveries at their disposal give evidence of the truth of the psycho-physiological hypothesis; in fact, this is their only working hypothesis sine qua non the very existence of these sciences.
The psycho-physiological hypothesis finds special support in the brilliant investigations of experimental physiology. The experiments of Munk, Ferrier, Hitzig, Brown-Sequard, Goltz, Schiff, and others clearly show the correlation of brain functions with psychic activity. They show, for instance, in animals that the physiological processes in the occipital lobes are correlated with vision, that those of the temporal lobe, especially of the superior temporo-sphenoidal convolution are correlated with hearing, that sensations of smell are concomitant with the function of the median descending part of the temporal lobes, that taste is probably correlated with the processes of the lower temporal regions, that tactual sensibility is intimately connected with the physiological processes of the motor zone; and the recent researches of Bianchi and Flechsig tend to correlate the highest psychic activity of man with the function of definite areas in the cortex.
Should we care to look for more proofs as to the validity of correlation of psychic with neural, or physical processes, we can also find it in another branch of experimental physiology, namely, physiological psychology. Thus Doctor Lombard by placing sensitive thermometers and electric piles against the scalp noted a rise in temperature during intellectual effort, such as calculation, recitation, composition. The temperature showed a marked rise exceeding 1° F. during an intense emotion. When intellectual activity rose in intensity there was also a parallel rise in temperature, thus the temperature was found to be higher, when poetry was recited silently than when the same was done aloud. Similar results were arrived at by Schiff in his experiments on dogs. He placed thermo-electric needles on the scalps of dogs; the sensations of the animals were then tested with different kinds of stimuli. It was found that whenever the stimulus was given and the sensation experienced, that a change was at once manifested in the cerebral and motor processes which was indicated by the deflection of the galvanometer. When the dog was lying motionless and a rolled up piece of paper was given to him, the galvanic deflection was small, when, however, a piece of meat was brought near the dog, the deflection became considerable. Galvanometric deflections concomitant with psychomotor activities have also been shown in the case of human subjects.
The ponograph is well adapted to demonstrate in a striking way to the doubting layman the intimate relation of physical and mental phenomena. The subject is put on a table, which is so delicately balanced that at the slightest alteration in the distribution of the weight of the subject, it tilts. Now it is found that when the subject is spoken to, or when making some intellectual effort, the table at once tilts possibly because of the increased blood supply to the brain and more especially on account of the motor reactions. Pneumographic, plethysmographic, carotido-graphic, cardiographic, automatographic, ponographic, and ergographic tracings show physiological changes concomitant with the slightest modification of psychic processes. As simple an instrument as the sphygmo-graph can demonstrate the same truth. A sphygmogram taken under mental activity differs from the one taken under mental repose.
All these facts, and many more could be adduced to establish on a firm basis the psycho-physiological hypothesis that psychic phenomena are accompanied with physiological or physical processes. The whole of recent psycho-physiological research work is based on the hypothesis that there is no psychosis without neurosis. The two are concomitant. Psychic and physical phenomena go hand in hand, the two processes run parallel to each other. Thus we find that psycho-physiological parallelism is a strictly scientific hypothesis.
The psychic and physiological series of changes are concomitant, parallel, but they do not stand to each other in relation of antecedent and consequent, they are not causally related. I take here the opportunity of emphasizing the non-causal relation of mental and physiological processes. It is usually taken for granted by many medical men, and even by some scientists, neurologists, physiologists, biologists, who do not happen to think out clearly the more theoretical aspects of their investigations, that brain processes are the direct cause of mental phenomena and that psychology therefore is nothing but a chapter in physiology. Study the brain and you will know all about psychic life. This view is certainly fallacious. A psychic fact as we have pointed out is radically different, different in kind from a physical, mechanical fact. One cannot, therefore, give rise to the other.
The reason why it is thought that physical processes give rise to mental, lies in the fallacious analogy taken from the law of convertibility and equivalence of energy in the activity of physical processes. Heat, it is reasoned, can be converted into electricity, electricity into magnetism, magnetism into motion, motion into sound or light, and the same may be done in reverse order; the energy of physiological processes therefore is converted into mental, or psychic energy. The whole reasoning is wrong. We must remember that what underlies all these different physical phenomena is various forms of molecular and molar motion, and when one order of physical phenomena passes into another, it is after all only the transformation of one form of motion into another form. Quite different is it in the case of the phenomena of consciousness. The activity of consciousness is not a form of motion, and the two therefore, cannot be converted into each other. Mental activity is but figuratively termed energy, just as a well reasoned argument may be characterized