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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 169

condition, but not so distinctly. There is a slight shallowing of the fissure
and an interlocking of the adjacent walls, but no distinct bridging gyrus.

In rare cases in the human brain the deep annectant gyrus in question
rises completely to the surface and cuts the fissure of Rolando into two
separate parts. I have never seen such a condition, although a very close
approach to it is observed in one of my negro brains. Wagner * described
for the first time such an interruption of theRolandic fissure in the brain of the
celebrated Physician, Professor Fuchs. Heschl,"f who examined no less than
2174 hemispheres, only found the anomaly in its complete form six times,
viz. five times in the male brain, and once in the female brain. Eberstaller
met with it twice in 200 brains. It is therefore a condition of extreme
rarity. Sernoff % figures a good example of this condition of the fissure of
Rolando in a right hemisphere (fig. 34).

III. Development.—The results at which I have arrived regarding the
development of the fissure of Rolando are based on the study of thirty-nine
hemispheres which I have collected between the fifth and seventh months
of development. I have also been supplied, through the kindness of Professor
Victor Horsley, with photographs of the series of brain specimens
in the Oxford Museum. Several of these show the fissure in its earlier
stages.

The view which is generally entertained regarding the development of
the Rolanclic sulcus pictures it beginning as a slight furrow midway between
the upper border of the hemisphere and the margin of the Sylvian fossa,
and extending gradually and continuously in an upward and downward
direction. That it may develop in certain cases this way I do not deny,
but I have no direct evidence to show that it does so. In one somewhat
advanced hemisphere—belonging to a brain approaching the seventh

* Vorstudien zu einer vassenschaftlichen Morphologie und Physiologie des ruenschlichen
Gehirns als Seelenorgan, 2 Abh., 1862, Tab. 1, s. 14.

f "Die tiefen Windungen des menschlichen Grosshirns und die Uberbriickung der Central -
furche," Wiener Medicinischer Wochenschrift, 1877, No. 41.

\ Bedki shitchai vidoizrueneniya forniy Rolandovoi borozdy i tsentralnykh izvilin mozga.
(A rare case of change of form of the Eolandic furrow and central convolutions.) Moskow, 1887.

EOTAL IEISH ACADEMY.-CUNNINGHAM MEMOIRS, NO. VII. [22]