NORMAL DEVELOPMENT OF EYE-
DOMINANCE COLUMNS
This section shows layer 4C cut 
transversely, from a newborn 
macaque monkey with an eye 
injected. The picture is dark 
field, so the radioactive label is 
bright. Its continuity shows 
that the terminals from each 
eye are not aggregated into 
stripes but are intermingled 
throughout the layer. (The 
white stripe between the 
exposed and buried 4C layers is 
white matter, full of fibers 
loaded with label on their way 
up from the lateral 
geniculates.)

    The obvious way to learn 
about ocular-dominance 
columns in the newborn was to 
check the distribution of fibers 
entering layer 4C by injecting 
an eye on the first or second 
day of life. The result was 
surprising. Instead of clear, 
crisp stripes, layer 4C showed a 
continuous smear of label. The 
autoradiograph to the left 
shows 4C cut transversely, and 
we see no trace of columns.