CORTICAL LOCALISATION AND FURROW FORMATION 
GEOFFREY JEFFERSON 
Victoria, B. C. (Late Demonstrator in Anatomy, University of Manchester) 
ONE FIGURE 
The study of cortical localisation, whether by the more popular 
microscopical methods of Brodmann, Campbell, Bolton, Mauss 
and others, or along the macroscopical lines laid down by Elliot 
Smith, has raised many points of great interest. Not the least 
important of these is the question of the relationship of the 
cerebral furrows to the various specialised areas. Anatomists 
are divided into two camps: Those who believe that the furrows 
are produced purely by growth antagonism and those who 
claim chief importance for the influence of local differentiation. 
It will be shown below that both of these factors have a marked 
influence, and it will be our present endeavor to examine just 
what value each of the two has, first in the primate brain and 
then in lower brains. | 
With regard in the first instance to cortical differentiation. 
It will be seen that this factor is unsatisfactory as the sole pro- 
ducer of furrows, for it does not always lead to furrow formation. 
Brodmann (4) has recently published surveys (fig. 1) of two of 
the lower monkeys (Hapale jacchus and Lemur niger), both of 
which have neopallial surfaces showing distinct histological 
areas. Yet neither of them has many furrows; Hapale jacchus 
has no sulcus centralis, for instance, although the animal possesses 
sharply defined motor and sensory areas, and this furrow is but 
dimly fore-shadowed in the Lemur named. If cortical special- 
isation was sufficient in itself to produce furrows, then any 
animal which had more than one area on its brain (and what 
animal has not?) should have corresponding furrows to limit 
the boundaries of those areas, or to be enfolded axially along 
them, to use Elliot Smith’s terminology. As we have just seen— 
and many other examples could be cited—this is not the case. 
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