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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 283

The various anatomists who have studied the sulci on the outer surface
of the frontal lobe have arrived at very different conclusions regarding
their homologies. Eberstaller* and Waldeyerf have both given a very
complete and exact account of these diverse opinions on this question, so
that it is merely necessary for me to allude very briefly to them.

According to Grratiolet and those who agree with him the sulcus rectus
is the representative in the apes of the sulcus frontalis secundus in man,
whilst the horizontal ramus of the arcuate sulcus is the sulcus frontalis
primus. On the outer surface of the frontal lobe of the apes according to
this theory, therefore, we have the same three tiers of convolutions which
are usually recognized in the brain of man, viz.—(1) a superior frontal
convolution between the mesial margin of the hemisphere and the horizontal
part of the sulcus arcuatus ; (2) a middle frontal convolution between the
horizontal limb of the arcuate sulcus and the sulcus rectus; and (3) an
inferior frontal convolution below the sulcus rectus.£

Pansch§ argued differently. The sulcus arcuatus he regarded as the
representative of the " ersten radiaren Primarfurche," which, according
to his view, is a compound furrow composed of the inferior prsecentral
and the second frontal sulci. He further believed that the sulcus rectus
is a furrow peculiar to the apes and completely absent in the human
brain.

We now come to those authors who consider that the inferior frontal
convolution in the apes is either absent or extremely feebly developed.
Thus Bischoff || regards the vertical limb of the sulcus arcuatus as the
sulcus praecentralis superior, and its horizontal limb as the sulcus frontalis
primus. The sulcus rectus, according to this author, is certainly not the

* Das Stirnbirn, p. 113. Leipzig, 1890.

f Das Gibbon-Hirn. Internationale Beitrage zur Wissenscbaftlichen Medicin. Virchow's
Festschrift. Band i., p. 35.

% Memoire sur les plis cerebraux de l'homme et des primates. Paris, 1854.

§ TJeber die typische Anordnung der Furchen und Windungen auf den Grosshirn-Hcmi-
spbaren des Menscben und der AfEen. Arcbiv fur Antbrop. Band in., 1869.

|| Die dritte oder untere Stirnwindung und die innere obere Scbeitelbogenwiridung des
Gorilla. Morpb. Jahr. Band til, 1882.

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