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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 115

II. Baboon.—Eight cerebral hemispheres examined.

In one, . . Insula perfectly smooth (PI. iv., fig. 8).
In one, . . Sulcus centralis Eeillii alone very feebly marked.
In four, . . Two furrows, viz. the sulcus centralis and sulcus postcentralis.
In two, . . Three furrows, viz. the prsecentralis, centralis, and postcentralis
.

III. Hamadrijas.—Two hemispheres examined.

In one, . I . Two furrows, viz. the sulcus centralis and postcentralis.
In one, . . Three furrows, viz. the sulcus prascentralis, the sulcus centralis,

and the sulcus postcentralis.

IV. Cercopithecus.—Four hemispheres examined.

In one, . . One furrow, the sulcus centralis.

In three, . . Two furrows, the sulcus centralis and the sulcus postcentralis.

V. Mangaby.—Four hemispheres examined.

In three, . . One furrow, the postcentral.

In one, . . Two furrows, the central and the postcentral.

VI. Cebus.—Five hemispheres examined.

In two, . . Insula smooth.

In two, . . One furrow, the central.

In one, . . Two furrows, the central and the postcentral.

From the foregoing it is, therefore, very evident that the most usual
condition of the insula in the lower ape is that in which it presents a
central and a postcentral furrow, with the three corresponding gyri.
The latter are very feebly developed. With the exception of the cebus, a
gyrus transversus can be detected in almost every case.

But another very striking difference between the human cerebrum
and the cerebrum of the ape is to be found in the relative size and
position of the submerged portion of the island of Reil. If we take the

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