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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 291

In the right hemisphere of this cerebrum (fig. 68) the sulcus frontalis
superior is in four separate and distinct pieces, which are placed one in
front of the other, a short distance from the mesial border. It therefore
presents in permanent form what is usually a transitory condition of the
corresponding furrow in the human foetus. It will be noticed, further,
that these distinct pieces of the furrow are oblique, and incline by their
anterior ends towards the mesial border of the hemisphere—the hinder
extremity of each lying at a lower level than the anterior extremity of
the one immediately preceding it. In those cases in the human cerebrum
where the constituent parts of the superior frontal furrow remain separate,
we have likewise observed this arrangement to be a characteristic feature.

A well-marked sulcus prsecentralis superior is present in connexion
with the basal or hinder part of the superior frontal furrow. The appearance
is such, however, that I am inclined to consider that the upper part
of the superior prsecentral furrow (p. c. s.) alone is joined to the superior
frontal sulcus, and that the lower part is in reality the hinder end of the
frontal sulcus carried backwards towards the fissure of Rolando. If this be
the case, the lower part of the sulcus prsecentralis superior is represented
by the furrow immediately below (&.).

The inferior prsecentral sulcus is well developed. It consists of a long,
vertical stem {p. c. i.), surmounted by a short horizontal ramus (h.).

The sulcus frontalis medius is in two portions (/. m.). The posterior
part is a short, straight furrow, which runs in the sagittal direction, and is
connected behind with the front branch of the ramus horizontalis of the
sulcus pra3centralis inferior. A very distinct deep annectant gyrus, which
is indicated in the drawing by a dotted line, marks the point of junction.
The front part of the sulcus frontalis medius is in every respect similar
to the corresponding part of the furrow in the human cerebrum. It is
sagittal in its direction, and traverses the anterior half of the middle
frontal gyrus. Towards its extremity it curves slightly downwards, and
finally ends at the superciliary margin by bifurcating into two widely
spread-out limbs, which together form a typical fronto-marginal sulcus of
Wernicke (w.). Throughout the whole course of this furrow there is not
the slightest indication of a deep annectant gyrus.

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