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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 113

Each of the four chimpanzee brains which I possess accords more or
less closely with the above general description, but there are individual
differences to be noticed in the degree of development of the different
convolutions and sulci. Further, on the under surface of the polar
projection of the island there is usually a small furrow which runs in the
line of the sulcus centralis and ends in the vallecula Sylvii. This limits a
distinct gyrus transversus or annectant gyrus, which extends from the forepart
of the insular pole to the orbital aspect of the frontal lobe. The furrow
itself is no doubt a detached part of the sulcus centralis.

In the orang there is no evidence of a gyrus transversus, or any other
direct bond of union between the polar projection of the island and the
under surface of the frontal lobe.

In the anthropoid, one transverse furrow on the deep surface of the
temporal pole is usually present, but this does not obscure the connexion
between the inferior limiting sulcus of the island of Eeil and the
incisura temporalis, and the continuity of the posterior insula with the
uncus.*

It is curious that while the anthropoid ape should be so absolutely

* Since the foregoing was sent to the printer I have received, throngh the courtesy of the author,
an interesting communication by Professor Waldeyer1 upon the Sylvian fissure and the insula in
the gibbon. This paper is illustrated by four beautiful drawings, which show that in this member of
the anthropoid group the sulcus centralis insula? is usually, although not constantly, present.
The author considers that the insula may be regarded in the gibbon as forming a single simple
convolution bent around a central furrow, and would seem to infer that we have here a condition
which may be regarded as affording us a " ground-plan," by means of which an affinity with the
carnivore type may be established. I do not agree with this view of the case, as may be inferred
from the foregoing. Waldeyer further remarks (p. 10) : " Die pars frontalis der Iusel biegt nun in die
dritte Stirnwindung um, die pars parieto-temporalis in die obere (erste) Schlafenwindung, grade
wie man es beim Meschen findet." Although he refers us to the drawings which he publishes for
confirmation of this statement, I cannot see any connexion whatever between the posterior insula
and the first temporal convolution. If there is, it must be of an entirely adventitious character
because, as we have seen, the true primitive connexion of this part of the island is not with the
temporal lobe but with the limbic lobe.

1 Sylvische Furche und Eeil'sche liisel des Genus Hylobates.—Sitzungsberickte der k. Preussischen Akad.
der Wiss. Berlin, Marz 19, 1891.

ROFAL IRISH A.CAJDEMT.-CCiN.VINGHAil MEMOIRS, NO. VII. [15]