Chapter II—Structure of the Brain.
Man a triple being—Materialists and illusionists misconceive him—Relation of the soul to the brain and body—The nervous system; illustration—Embryonic condition—Anatomical descriptions unsatisfactory and the phrenological school incorrect—Exterior view of the brain in the head, illustrated and described—The cerebrum, cerebellum, and tentorium—Interior view of the base of the skull—Bones of the head illustrated—Division of the brain into lobes and convolutions, with illustration—Frontal, middle, parietal, tempero-sphenoidal, and occipital—Anatomical plan or grouping of convolutions differs from their actual appearance—View of the superior surface illustrated—Difference between the irregular convolutions and the angular maps—View of the inferior surface of the brain—Illustration and description of the parts—Interior view of section on the median line—Divided and undivided surfaces-Corpus callosum explained—The two brains and their diagonal relations to the body—Penetrating and describing the lateral ventricles—The serum in the brain—Variations of serum and blood—Variations in hydrocephalus and insanity—Our power to modify the brain and change our destiny—Power of education—Responsibility of society—The lateral ventricles the centre of the brain—Base of the ventricles, the great inferior ganglia of the brain, corpora striata, and thalami—Their radiating fibres inclosing a cavity—The thalami and their commissure and third ventricle—The medulla oblongata, cerebellum, and arbor vitæ—The pons Varolii and crura of the brain—the corpora quadrigemina, pineal gland, fourth ventricle, and calamus scriptorius.
Man is essentially a triple organization, consisting of the permanent psychic being, intangible to our external senses, but nevertheless so distinctly recognized internally by consciousness and externally or in others, by intuition and understanding, that the psychic is as well understood and known as the physical being. This being is the eternal man—the material body being its temporary associate.
The physical being, or material form, consists of the portion directly and entirely occupied by the psychic existence—which is called the brain or encephalon, and is in life also beyond the reach of our senses in the interior of the cranium—and the non-psychic structure, the body, which, though not the residence of the soul, has so intimate and complete a connection with the entire brain that during active life it feels as if it were the actual residence of the soul, so far as sensation and action are concerned.
The soul, or psychic being, has external and internal perceptions (for which it has cerebral organs). When the former predominate too greatly, the human body and all external objects are realized most vividly, and the reality of psychic life is not so well realized or understood. Hence persons so organized are disposed to materialism, and either doubt the existence of their psychic being, or are indifferent to it.
On the other hand, those in whom the interior faculties predominate too greatly vividly realize their psychic life, but have more vague and feeble conceptions of material objects, including their own bodies, and attach undue importance to the imaginary and subjective in preference to the objective. The materialists and the illusionists, however, are not entirely composed of these two classes of subjective and objective thinkers. The majority consists of persons of moderate reasoning capacity, who simply follow their leaders.
In making a critical distinction between the psycho-organic brain and non-psychic body, the former may be confined strictly within the cranium, leaving the exterior portions of the head as a part of the non-psychic body; but as they are more intimately associated with the brain than any part below the neck, this distinction is not important; and if the whole head, as the environment of the psychic brain, be grouped with it, it may not lead to any material error. The brain is intimately associated with the entire physical person by twelve pairs of cranial or cerebral nerves, and by the spinal cord, which descends from the base of the brain through a great foramen or opening midway between the ears, and while passing down the spinal column gives off thirty pairs of nerves.
The cranial nerves are all for the head, except the pneumogastric or lung-stomach nerve, which belongs to the organs of respiration, voice, and digestion; and the spinal nerves are all for the body, except a few which ramify in the neck and in the scalp.
The entire nervous system is so instantaneously prompt in conveying to the brain the impressions which originate feeling, and in conveying from the brain the nervous energies that produce voluntary motion and modify all the processes of life, that we feel as if we had sensation and volition in every part of the body; or, in other words, that our conscious existence was in the body; but we rationally know that the sensation and volition occur in the brain, for neither sensation nor voluntary motion can occur if the nervous connection with the brain is interrupted by compression and section, or if the brain itself be sufficiently compressed. When the brain is exposed by an injury of the cranium, the pressure of a finger suspends all consciousness and volition, making a blank in the life of the individual.