CORTICAL LOCALISATION 295 
lodging the newly acquired functions has not been accom- 
panied by a proportionate increase in the intra-cranial space 
provided. 
A study of Brodmann’s interesting table (4) (see next page) in 
full shows a remarkably gradual and progressive diminution in 
convolutioning as we descend through the primates to the lowest 
monkeys. It is therefore probable that the factors in furrow for- 
mation are the same and are constant throughout the primates, 
otherwise the downward procession would not be so orderly. 
The probable cause of this is to be found in the fact that in the 
primates the cranial capacity remains relatively more or less con- 
stant, whilst the surface area to be accommodated gradually 
increases from the Lemurs to man, so that more and more fur- 
rows arise. 
The new areas that make their appearance in the anthropoids 
are the association areas. In 1913 the writer (1) (2) (3) pointed 
out that the parietal field was a new acquisition in human and 
anthropoid brains and therefore that the furrows traversing this 
area were new formations too and could have no homologies on 
lower brains. Ingalls (6) has since confirmed this. The pro- 
simian neopallium is almost entirely composed of the motor and 
the various sensory areas, each surrounded or contiguous with 
its corresponding “psychic” area (Flechsig and Bolton). Whilst 
in the higher brains these areas become widely separated nota- 
bly by the development of the posterior association field. In 
spite of the appearance of this large new area behind the cen- 
tral suleus the furrow is placed further back (more caudally) 
on the human brain than on the lower ones. Brodmann (5) 
has shown this to be due to the great increase in extent of the 
regio frontalis (proper). So that with these new areas to be 
accommodated it is not surprising that the human brain should 
be more highly convoluted than the lower, since the intra- 
cranial space has not increased coincidentally with it. It must 
be granted that when furrows do appear they tend to do so at 
the edges of the specialised areas, as Elliot Smith (7) was the 
first to point out. Difference of structure necessarily denotes 
a difference of texture, as we know in civil life from our experi- 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 25, NO. 3 
