THK VISUAL PATHS. 



-8 



AS 



MS. 



FIG. 16. Diagram of the visual paths (from Vialet, modified by Osier). OP.K, 

 optic nerve; OP.C., optic chiasma ; OP.T., optic tract; OP.R., optic 

 radiation; GEN., geniculate body; THO., optic tbalamus ; C.QU., corpora 

 quadrigemina ; C.C., corpus callosum ; V.S., visual speech centre; A.S., 

 auditory speech centre ; M.S., motor speech centre. A lesion at 1 causes 

 blindness of that eye ; at 2, bi-temporal hemianopia ; at 3, nasal hemianopia. 

 Symmetrical lesions at 3 and 3' would cause bi-nasal hemianopia ; a lesion at 4 

 hemianopia of both eyes, with hemianopic pupillary reaction ; at 5 and 6, 

 hemianopia of both eyes, pupillary reflexes normal ; at 7, amblyopia, 

 especially of the opposite eye ; at 8, on left side, word blindness. 



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