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tively, is not, has merely a smattering of physical knowledge. He says, "I know, because, etc." The man who has studied deeper, says: "There is a law of psychic force beyond the conception of physical sense, which physical science cannot reach." He has a courage to say, "I do not know." There is no doubt but that there is a psychico-chemical reaction in the brain, which can give a reaction in consciousness,-it is not matter.

Area of
Sensory
Organs.

When the belief that the cerebrum is the organ of thought, was reasonably established, the question naturally arose as to whether different parts of the cortex have different functions, corresponding to different mental faculties. Accordingly many systems of phrenology developed. Gall, a physician in Vienna, devoted his entire life to an earnest effort to establish his belief that different faculties of the mind are mediated through different parts of the brain. He conceived that the more developed any mental faculty, the larger will be that part of the

brain representing it, and, therefore, that since the cerebrum fits closely in the skull, the relative prominence of parts of the cerebrum may be determined by a study of the exterior of the skull. He did not take into consideration here that brains, small in area, may have deeper convolu

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FIG. 15. Shows the probable location of the chief motor and sensory areas of the cerebral cortex.

tions, hence contain more cortical surface

and more gray matter.

The most recent physiological conclusions modify Gall's theory. It is now be

lieved that motor movements and sensory impressions, for different parts of the body, are acted upon by localized centers in the brain, as shown by Fig. 15, but that these different centers are intimately associated, and, to a certain extent, dependent upon each other for full functional activity. Fritsch and Hitsig in 1870 exposed the brain and applied an electrical stimulus to different cortical areas;-upon stimulating one area a distinct and constant movement of the limbs resulted; stimulation of another area resulted in a movement of the arm and the hand, another the face, etc. It is not known whether the sensory areas correspond to the motor areas, but it is known that the poise of the nerves of the body re-act upon the mental poise,-e. g.: If one assumes a physical attitude of despondency, the brain takes on a corresponding poise; if one assumes a bodily attitude of courage and uprightness, one is filled with courage and self-respect.

It may be that it takes generations and even centuries for character of thought to

so develop localized centers as to change the shape of the skull, but in the dispersion of the races, the Ayrans, whose minds turned to agricultural pursuits, developed a characteristically shaped skull; the Nomads, who lived wandering lives, another; and the Hamitic race another, supposedly due to the distinct character of thought attendant upon the nature of their occupations.

The brain center for vision, as shown in Fig. 15, is, as demonstrated by Munk, Ferrier and others, in the occipital lobes; if the occipital lobes be removed, total blindness results. Defect in the right eye would be felt most in the left occipital lobe, because of the crossing of the nerves.

Defective vision often causes pain at the base of the brain, because the optical nerve ganglia are here.

The location of the auditory area, as demonstrated by Munk and Ferrier, is in the temporal lobes,-ablation of these lobes being followed by complete loss of hearing. It is probable that the auditory

nerve fibres cross, as do the visual nerves, to the opposite sides of the cerebrum.

The peripheral end organs of smell consist of the olfactory epithelium in the upper portion of the nasal chamber.

Nothing is definitely known of the origin of the nerves of taste, but this area supposedly lies near the olfactory area.

Cerebellum.

The cerebellum is often spoken

of as the "little brain." It is situated within the part of the skull immediately back of the ears. Its average weight is about 54 ounces.

In the cerebellum, the proportion of gray matter is greater than in the cerebrum. It is arranged in about the same way, the convolutions in the cerebrum being deeper. In addition to the cortex, the cerebellum contains several masses of gray matter in the interior.

The exact function of the cerebellum is not known, but it is known that the cortex of the cerebellum presents a very complex reflex arc. The theory introduced by Flourens is generally accepted:-It is sup

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