GROWTH OF THE CEREBRAL CORTEX 29 
ences noted may be correlated with differences in function, but 
at present we shall consider only those which appear in the oc- 
cipital cortex, that is, at localities IV, V, XII, and XIII. There 
is reason to think that the eye and the visual apparatus in gen- 
eral are less well developed in the Albino than in the Norway rat. 
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Chart 6 Giving the corrected thickness of the cortex of the Norway rat in 
the horizontal section. Individual entries for the cortical thickness at localities 
IX and XIII] and the average thickness of the horizontal section (localities IX, X, 
XI, XIf and XIII) are given. Based ontable 6. ° Cortical thickness at locality 
IX. Corrected. *Cortical thickness at locality XIII. Corrected. * Average 
thickness of the horizontal section. Corrected. 
The visual cortex of the rat is at the occipital.end of the brain 
(Ferrier, 86) and would probably be underdeveloped in the Al- 
bino in which vision was less perfect. The relatively less thick- 
ness of the cortex in the localities IV, V, XII and XIII in the 
Albino brain would therefore fit with the diminished visual func- 
tion in this form. 
