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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 99

Certainly, in the adult the condition of affairs presents this appearance
(fig. 27) ; but we shall see later on that a study of the development of
the parts clearly indicates that the connexion is not with the temporal lobe,
but with the great limbic lobe.

There is thus a very close correspondence between the convolutions
and sulci on the surface of the island of Reil and those on the lateral
surface of the hemisphere. The two central convolutions (i. e. gyrus brevis
tertius and gyrus longus of Eberstaller) correspond with the two central
convolutions (ascending frontal and ascending parietal), and the three
fissures, viz. the sulcus prsecentralis Reillii the sulcus centralis, and the
sulcus postcentralis Reillii, are in every respect comparable with the
sulcus prsecentralis inferior, the fissure of Rolando, and the vertical limb
of the intraparietal fissure on the surface of the mantle. It is true that
we cannot regard these corresponding convolutions and sulci as being
directly continuous with each other, but still in many cases something
which approaches very nearly to continuity occurs. Thus it is well-known
that the inferior prsecentral sulcus, the fissure of Rolando, and the intraparietal
sulcus are not unf requently carried downwards so as to cut into the
fronto-parietal operculum and open into the Sylvian fissure. Eberstaller
has pointed out that when this occurs in the case of the fissure of Rolando
the condition is brought about by the extension upwards round the lower
margin of the operculum of a small variable furrow which he terms the
inferior transverse sulcus of the fissure of Rolando. This undoubtedly
belongs to the same system as the fissure of Rolando and the sulcus centralis
Reillii; in other words, it is to be regarded as the connecting link. The
extension of the intraparietal into the fissure of Sylvius is effected in
precisely the same manner. A small variable opercular furrow extends
upwards into it and acts as a loose bond of union between it and the
postcentral sulcus of the insula. I am not able to speak with the same
certainty of the two prsecentral sulci. These two furrows, the one on
the surface of the insula and the other on the surface of the mantle, are
more strongly marked in the foetus than in the later stages of development,
and consequently their relations in the adult cannot be studied with the same
precision. When the inferior pra>central sulcus on the surface of the

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