Freiburger historische Bestände - digital

De. Cunningham—Surface Anatomy of the Primate Cerebrum. 95

definition of an " anterior limb," in so far that they are not developed as
primitive deficiencies in the orbital operculum. They do not appear until
the eighth month, when the orbital operculum is well formed. A slight
notch on the margin of the operculum is all that indicates the presence of
the external orbital limb at this stage. This gradually deepens until it cuts
right through the operculum.

Eberstaller has called attention to the connexion which exists between
the external orbital limb and the gyrus accessorius of the island of Reil,
and has shown that even when the fissure is absent on the surface it may
be recognized on the deep surface of the orbital operculum. To this
aspect of the question we shall require to return when we are considering
the convolutions on the surface of the insula.

IV. Convolutions and Sulci on the Surface of the Insula.—The

admirable description of the gyri and sulci on the surface of the island of
Reil which has been given by Eberstaller* leaves little to be desired, in so
far as the adult brain is concerned. He points out that the insula is
divided into an anterior and a posterior part, which are quite distinct from
each other, by a sulcus which lies in the same plane, and presents the same
direction as the fissure of Rolando. This furrow had previously been noted
by Hefftlerf and Guldberg,^ and the latter author has suggested for it the
very appropriate name of sulcus centralis insulas, which indicates not only
its central position in the island of Reil, but also its relation to the central
fissure on the outer face of the hemisphere mantle. The portions of the
island of Reil which lie in front of, and behind this sulcus Eberstaller has
termed the insula anterior and the insula posterior.

It will be necessary for me to state briefly the further points in the
anatomy of the island of Reil, which have been elucidated by Eberstaller,

* " Zur Anatomie und Alorphologie der Insula Reillii," Anatomischer Anzeiger, No. 24,
15 Nov., 1887, p. 739.

f 1 ide a Report upon Dr. Hefftler's Inaugural Dissertation upon " Die Grosshinrwindungen
des Meuschen und deren Bcziehungen zum Schadeldach," by Prof. Landzert, in the Archiv fur
Anthropologic, Band x., 1878.

t " Zur Morphologie der Insula Reillii," Anatomischer Anzeiger, No. 21, 1. October, 1887,
p. 659.