Freiburger historische Bestände - digital

100

Cunningham Memoirs.

mantle communicates with the fissure of Sylvius, it does so by joining either
the inferior transverse furrow of the fissure of Rolando, or the sulcus dia-
gonalis of Eberstaller. It is possible that the latter furrow constitutes the
connecting link between the two prsecentral sulci. When we come to
deal with the development of the sulci on the insula we shall see that
the prsecentral sulcus becomes slightly shifted in a forward direction, so
that it does not accurately coincide in its direction in the adult with the
corresponding furrow of the frontal lobe.

But further, the inferior frontal convolution stands in close connexion
with the portion of the anterior insula which is placed in front of the
prsecentral sulcus of the island of Reil. Thus the gyrus brevis primus in
its upper part lies under cover of the pars triangularis, and not infrequently
pushes itself across the upper limiting sulcus of Reil to form a direct
connexion with this part of the lower frontal convolution. The gyrus
accessorius stands in precisely the same relation to that part of the orbital
portion of the inferior frontal convolution which lies between the anterior
horizontal limb of the Sylvian fissure and the posterior extremity of the
external orbital sulcus. The connexion between the sulcus which limits
the gyrus accessorius below and the external orbital sulcus on the orbital
face of the frontal lobe is also apparent. This sulcus is continued on to the
deep surface of the orbital operculum, and in certain cases cuts right
through it to form the external orbital limb of the Sylvian fissure.
Benedikt terms this limb the u hinder piece" of the orbital sulcus, and
remarks that he has observed the two fissures to become continuous with
each other. This condition I have never seen; but be this as it may, I
regard the external orbital limb of the Sylvian fissure in the same light as I
do the inferior transverse sulcus of the fissure of Rolando of Eberstaller.
It is a secondary fissure in the operculum which is to be regarded as an
intermediate piece between the sulcus on the insula which bounds the gyrus
accessorius below and the external orbital sulcus on the orbital face of the
frontal lobe.

But a very considerable amount of variation is to be noted in the
arrangement of the gyri in the forepart of the insula, and it is of
importance to observe that this goes hand in hand with variations in the