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PHYSIOLOGY. 



Visual Field. The boundary of the visual field of white light 

 crosses the upper vertical meridian at 55, the median meridian at 

 60, the lower vertical meridian at 70, and the external meridian 

 beyond 90. The field for yellow light is within that for white, the 



Fig. 371. Diagram of Right Homonymous Hemianopsia and of the 

 sites of lesions which may cause it. (BALL.) 



RE, Right eye. LE, Left eye. ON, Optic nerve. C, Chiasma. OT, Optic 

 tract. Th, Thalami optici. G, Corpora geniculata. Q, Corpora quadrigemina. 

 RC, Right cuneus. OR, Optic radiations. 



field for blue light within that for yellow, the field for red within 

 that for yellow, and the field for green is much smaller. 



Pathological. ARGYLL-KOBERTSON PUPIL. Here there is no 

 contraction of the pupil to light (no light-reflex); but it does con- 

 tract when the accommodation is called into play for near objects, 



