Freiburger historische Bestände - digital

242

Cunningham Memoirs.

as Pansch has shown the sulcus postcentralis inferior and the sulcus horizontals
very frequently appear as one continuous furrow.

4. The sulcus postcentralis inferior usually appears first; then the
ramus horizontalis and ramus occipitalis; and last of all the sulcus postcentralis
superior.

5. In Cebus there is no sulcus postcentralis superior; it is present,
however, in most of the old world apes, e. g. the baboon, macaque, gibbon,
chimpanzee, orang, and gorilla.

6. In the chimpanzee and orang there is reason to believe that this
segment of the postcentral sulcus consists of two elements—one placed
above the other.

7. Eberstaller's third and lowest segment of the postcentral sulcus (viz.
the sulcus postcentralis transversus) is not only present in man but also in
the majority of the old world apes.

8. In the apes the intraparietal sulcus is deeper than the fissure of
Rolando; the opposite is the case in man. This would seem to indicate
that the morphological value of these sulci is different in man and the apes.
The phylogeny and ontogeny of these furrows are in apparent variance
with each other. The fissure of Rolando appears first on the developing
cerebrum of the human foetus, yet it is the intraparietal sulcus which first
makes its appearance in the evolution of the primate cerebrum.

9. Putting aside for the present the ramus occipitalis we meet in the
adult human brain with every possible form of combination of the
remaining three segments of the sulcus.

10. The most common combination is that in which they are all (superficially
at least) connected together. This was present in 60-3 per cent, of
the adult hemispheres examined.

11. In man there appears to be a general tendency towards a union of
the two originally distinct postcentral elements of the sulcus and a divorce
from the lower of these of the ramus horizontalis.

12. It seems very probable that a more extended investigation into
the arrangement of the intraparietal sulcus may establish marked racial
and sexual distinctions in the manner of grouping of its different
segments.