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Lectures on Mental Diseases.

LECTURE I.

INTRODUCTORY.

THE PHYSICAL BASIS OF THOUGHT.

Advance in the Study of the Minute Anatomy of the Brain-Lobes, Convolutions and Fissures of the Brain-The cortex cerebri-Grey matter of the Brain-Central Ganglia-Optic Thalami-The Striate Bodies-Two Kinds of Nerves, the Sensory and Motor-Anatomy of the Nerves-Anatomical Arrangements of the End Organs of Sense-Functions of the NervesThe Transmission of Irritations to and from the Cortex-Functions of Nerve-cells and Nerves Contrasted-Transformation of Irritations into Sensations-The Thought-process in its Relation to the Molecular Activities of the Nerves and Cells of the Cortex-The Evolution of Sensations, Perceptions, Thoughts, Purposes, and Opinions-The Mind, Personality, Ego-Views of Different Authors-Nerve-energy-Agents which Affect it-Measurement of its Degree of Action-Derangement of its Normal Action the Initial Element of Insanity.

No greater advance has been made in the study of the minute anatomy of any organ or part of the system within recent years than in that of the brain and spinal cord. This has been stimulated in the first instance by the desire to understand more fully and perfectly the relation which had long been surmised to exist between disordered mental

states and diseases of the brain, but which it had never been feasible to demonstrate. The microscope and the discovery of means whereby brain tissue can be prepared for observation, have now made it possible to study some of the pathological conditions to which it is subject. It, therefore, may be regarded as important, in introducing you to the study of mental diseases, to call your attention to some of its component parts and ganglia; and also to allude to the complexity and arrangements of the elements of which it is composed. While a résumé of the knowledge of the anatomy and physiology of the whole nervous system is most desirable and important as preliminary to the study of insanity, yet the subject is too large for a lecture. An attempt at a complete presentation would necessarily cover too much of the space allotted to me in these lectures. It will, therefore, be my purpose to present only the briefest enumeration and description of some of those parts of the brain and nerves which are supposed to be most intimately concerned, through their physiological functions, in mental processes. For further and more perfect account of the anatomy and physiology of the brain and spinal cord, I refer you to the works of Obersteiner, Hughlings Jackson, Bevan Lewis, Meynert, Luys, and others, whose recent studies have so greatly enriched our knowledge of this subject.

The nervous system may, then, for convenience of study, be divided into two portions: First, the encephalon, or brain proper, with the spinal cord; and second, the nerves which pass to and from the brain to all portions of the general system, covering every point upon its whole surface. The brain itself is composed of two hemispheres, symmetrically constituted and arranged, which are united by a band of white fibres constituting the commissures, by means of

which they are brought into the most intimate connection, establishing thereby a sort of double brain. Each hemisphere is mapped out into lobes and convolutions, which are bounded more or less definitely by lines or fissures. While the arrangement of the fissures is not invariable, yet it is

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generally so definite as to be easily recognized, especially in the more important ones. The principal fissures are: 1. Fissura Sylvii or the great lateral fissure. 2. Sulcus Rolandi, or the transverse fissure. 3. Fissura occipitalis, or the perpendicular occipital fissure. 4. Fissura calcarina, or

the horizontal occipital fissure. Besides these there are other minor or secondary fissures. The frontal lobe has four of these fissures, two of which are perpendicular, and two lon

FIG. 2.

VIEW OF THE BRAIN FROM ABOVE.

gitudinal; and also four convolutions; the anterior central, the middle, the lower, and upper longitudinal. The parietal lobe is divided into the superior and inferior, and has four

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