THE VISUAL PATHWAY
The initial stages of the 
mammalian visual system have 
the platelike organization often 
found in the central nervous 
system. The first three stages 
are housed in the retina; the 
remainder are in the brain: in 
the lateral geniculate bodies 
and the stages beyond in the 
cortex.

    We can now adapt our 
previous diagram to fit the 
special case of the visual 
pathway. As shown in the 
illustration at left, the 
receptors and the next two 
stages are contained in the 
retina. The receptors are the 
rods and cones; the optic nerve, 
carrying the retina's entire 
output, is a bundle of axons of 
the third-stage retinal cells, 
called retinal ganglion cells. 
Between the receptors and the 
ganglion cells are intermediate 
cells, the most important of 
which are the bipolar cells. The 
optic nerve proceeds to a way 
station deep in the brain, the 
lateral geniculate body. After 
only one set of synapses, the 
lateral geniculate sends its 
output to the striate cortex, 
which contains three or four 
stages.