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Cunningham Memoirs.

are altogether peculiar. These may be studied in Plate vni., in which a
model of the head of a Cebus capucinics, with the brain exposed in situ, is
depicted. In the cranium of this animal the coronal suture is extremely
oblique, and the bregma is placed very far back. In consequence of this
the suture crosses the upper portion of the fissure, and the upper end of the
latter, therefore, comes to lie a short distance in front of the bregma. The
index obtained is 5-3. Further, owing to the straight course pursued by
the fissure, it comes about that its lower end is placed very far behind the
coronal suture. The lower corono-Rolandic index is no less than 16*3.
Fere" * has also called attention to the unusual relations presented by the
fissure of Rolando to the cranial wall in Cebus.

VII. Rolandic Angle.—By the " Rolandic angle" I mean the angle
which is formed by the meeting of the upper end of the sulcus with the
mesial plane. If we were to divide a cerebral hemisphere into an anterior
and posterior portion along a line stretching from the point where
the sulcus oversteps the upper border of the hemisphere to the lower end
of the fissure, the angle which would then be formed by the cut surface
and the mesial surface of the anterior segment would constitute the
Rolandic angle.

Several authors have sought to establish a sexual distinction b}r means
of this angle. Huschka remarks : " On an average the fissure of Rolando,
with its bounding central convolutions, stands more perpendicularly in the
female than in the male." Rudinger says: " The more transverse direction
of the fissure of Rolando, and the bounding central convolutions,
appears in the female foetal brain a striking arrangement. But as the
oblique direction of the central convolutions in the female foetal brain, and
the transverse in the male, likewise occur, I might provisionally entertain
the supposition that these differences might be produced less through sex
than through differences in the shape of the head." His pupil, Passet, is
less cautious, and states dogmatically that "the angle which the fissure

* " Contribution k V etude de la topographie cranio-cerebrale cbez quelques singes," Journal
de V Anat. et Hist., vol. xviii.