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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 85

number of cases of this kind which he had observed in lunatics, criminals,
and in negroes. I am so fortunate as to possess twelve cerebral hemispheres
of negroes, which were presented to me by the late Dr. W. Hart, of Sierra
Leone. In only one of these is there any exposure of the island of Reil,
and this to a very small degree. On the other hand, the pars triangularis
is in the great majority particularly well developed, and in no respect
different from the condition in which it is found in the European. In the
orbital operculum, however, there is a manifest deficiency. Not only does
this fail to extend so far inwards upon the orbital face of the frontal lobe,
as in the case of the European, but it also appears to be shorter.

I quite agree, therefore, with the following remarks on this subject,
which have been made by Rudinger* : " Ob dieses Offensein der Fossa
Sylvii zur Zeit der Geburt eine bleibende Anordnung bei niederen Racen
ist, muss so lange als offene Frage betrachtet werden, bis eine grossere
Anzahl Gehirne von niederen Racen unversehrt der Untersuchung zugang-
lich sein wird. In Alkohol konservirten Praparaten an welchen die Pia mater
entfernt wurde konnen iiber diesen Punkt nur ungeniigenden Aufschluss
geben."

The foregoing account may be regarded as giving the more usual course
which is followed in the development of the opercula which close in the
Sylvian fossa, but I have referred to cases in which, towards the end of the
fifth month, the originally rounded anterior angle of the open fossa becomes
acute and pointed (PI. il, fig. 11). When this occurs, the usual course is
that development goes on without the formation of a frontal operculum.
The temporal, frontoparietal, and the orbital opercula alone appear, and
only one anterior limb of the Sylvian fissure is formed. This is interposed
between the contiguous margins of the fronto-parietal and the orbital
opercula (fig. 25, iv.).

Broca has given a diagram of the development of the Sylvian opercula
which I take the liberty of reproducing (fig. 26). It differs in several
essential points from mine. He shows a retention of the primitive anterior
angle of the fossa (c), and yet he indicates the development, not only of a

* "Zur Anatomic dee Sprachcentnmis." Stuttgart, 1882, p. 5.