Freiburger historische Bestände - digital

296

Cunningham Memoirs.

There is one sulcus in the frontal lobe of the human cerebrum which
never occurs in the cerebral hemisphere of the apes. I refer to the sulcus
frontalis mesialis, which appears in the first frontal gyrus in the form
of two or three separate furrows which occasionally run together. It
presents a degree of development comparable with that of the sulcus
frontalis superior in the chimpanzee, and I have already alluded to
the fact that it is more strongly marked in the European than in the
Negro.

XI. Exposed part of the Insula and the Sulcus Fronto-orbitalis in
the Apes.—The great majority of observers are at one in regarding the
inferior frontal convolution in the anthropoid brain to be represented by the
small loop of cerebral surface which is bent around the so-called anterior
limb of the Sylvian fissure. As early, however, as 1876, Pansch advanced
a different view. He says: " What Bischoff, therefore, claims to be the
third frontal convolution in the anthropoids is, in my opinion, in its
upper part only a small piece of the gyrus frontalis inferior, and in
its under part a piece of the uncovered insula."* Kohlbrugge,+ in his
study of the brain of the gibbon, has arrived at similar conclusions, and
I now desire to state that, in this matter, I fully agree with both of
these observers.

Pansch is in error, however, in so far that he regards the sulcus
fronto-orbitalis as the representative of the anterior limb of the Sylvian
fissure. There is no anterior limb of this fissure in the anthropoid brain
and there can be no such limb. A Sylvian limb can only be formed by
the contact of the opposed margins of two adjoining Sylvian opercula.
The posterior limb is formed by the apposition of the fronto-parietal
and the temporal opercula. There is no frontal and no orbital operculum
in the anthropoid apes, and therefore there can be no anterior

* " TTeber die Furchen und Windungen am Gehirn eines Gorilla," Abhandlungen aus dem
Gebiete der JSTaturwissenschaften berausgegeben vom xiaturwissenscbaftlichen Verein zu
Hamburg-Altona—; Bolau und Pansch, p. 22. Hamburg, 1876.

•j- " Yersucb einer Anatomie des Genus Hylobates," Zoologiscbe Ergebnisse einer Reise in
Niederlandiscb Ost-Indien. Band n., p. 191. Leiden, 1891.