TOPOGRAPHIC REPRESENTATION
A microscopic cross-sectional 
view of the optic nerve where it 
leaves the eye, interrupting the 
retinal layers shown at the left 
and right. The full width of the 
picture is about 2 millimeters. 
The clear area at the top is the 
inside of the eye. The retinal 
layers, from the top down, are 
optic-nerve fibers (clear), the 
three stained layers of cells, 
and the black layer of melanin 
pigment.

    Even before further research 
became possible, we were not 
completely ignorant about the 
parts of the brain involved in 
vision: the geography of the 
preliminary stages was already 
well mapped out (see the 
illustration to follow). We knew 
that the optic-nerve fibers 
make synapses with cells in the 
lateral geniculate body and that 
the axons of lateral geniculate 
cells terminate in the primary 
visual cortex.