Nervous and mental diseases . ision centers of the cuneus are in turn brought byconnecting fibers into relation with higher centers for visual memories,probably situated in and about the angular gyri of the parietal these higher visual centers both eyes are represented in each hemi-sphere. The parietal centers probably freely communicate through thecallosal crossway. Injury to the left parietal region in right-handedpersons produces loss of visual word-memories; or word-blindness, butdoes not necessarily cause hemianopsia. The fibers which supply the macula lutea of the retina occupy
Nervous and mental diseases . ision centers of the cuneus are in turn brought byconnecting fibers into relation with higher centers for visual memories,probably situated in and about the angular gyri of the parietal these higher visual centers both eyes are represented in each hemi-sphere. The parietal centers probably freely communicate through thecallosal crossway. Injury to the left parietal region in right-handedpersons produces loss of visual word-memories; or word-blindness, butdoes not necessarily cause hemianopsia. The fibers which supply the macula lutea of the retina occupy at theapex of the orbit the central portion of the optic nerve in close proxim-ity to the central artery and vein. They then become superficial on theouter side of the nerve and proceed in this position to the back of theeye. Aneurysm of the central artery or axillary inflammation of thenerve about the artery may so involve them that blindness of the centerof the field develops. This condition of central blindness, or central. Left. Eight. Fig. 32.—Scotomata in toxic amblyopia, consisting of increased size of blind spots, whicb are represented by the darker shading. scotoma, is also common in tobacco and alcoholic amblyopia. The poisonseems to have the greatest effect on the most used and consequently mostsensitive fibers or their related parts. The loss of vision is sometimes limited to a quadrant of the quadrant in the field is bounded practically by lines horizontal andvertical to the fixing point, which itself is spared. A case originallypresenting hemianopsia may eventually recover in part and a quadranticloss alone remain. It is probable that these quadrants are speciallyrepresented in the occipital cortex. In organic hemianopsia usually theseeing half of the field is also more or less peripherally reduced. Theblind portion of the field may not be uniformly affected, some fractionalvision remaining at various points. Rarely cases have been noted inwhich there
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