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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 305

seen as in man with this exception: the superior frontal gyrus is never split
into two by a sulcus frontalis mesialis.

23. The inferior frontal convolution of the apes is very different from
that in man.

24. The frontal and orbital Sylvian opercula are completely absent in
the apes.

25. Consequently, as Pansch and Kolhbriigge have maintained, a
portion of the island of Eeil is uncovered and exposed on the surface
of the cerebrum.

26. The sulcus fronto-orbitalis of the apes corresponds to the anterior
limiting sulcus of the island of Reil in man.

27. There are no anterior limbs of the Sylvian fissure in the anthropoid
apes. The so-called anterior limb of the Sylvian fissure corresponds to
the anterior free border of the fronto-parietal operculum.

28. About the seventh month of foetal life the inferior prsecentral sulcus
of the human brain attains a position which it maintains unaltered throughout
all the subsequent stages of growth ; previous to this it is placed
relatively further back on the surface of the hemisphere.

29. At first it is placed in front of the coronal suture. The sutural line,
however, moves forward so that the sulcus ultimately comes to lie behind it.

30. In the ape-cerebrum the inferior pra^central sulcus lies relatively
much further forwards than in the cerebrum of man. It may be placed
either immediately subjacent to, or in front of, the coronal line.

ROYAL IRISH ACADEMY.-CUNNINGHAM MEMOIRS, NO. VII,

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