Freiburger historische Bestände - digital

102

Cunningham Memoirs.

fig. 21, i); the inner gyrus is continuous with the hinder part of the
insula (PI. i., fig. 21, 2), and lies close to the outer side of the front end
of the uncus (PI. i., fig. 21, 3), which, as is well known, very early takes
shape (PI. il, figs. 2, 7, 22, and 23; and PL 1., figs. 21, 22, and 23).
These may be termed the primitive polar gyri of the temporal lobe,
and in the figures in Plates 1. and 11. in which they are depicted they are
marked 1 and 2, whilst the uncus is marked 3. A faint furrow intervenes
between them, but they are rendered more conspicuous by their own
prominence than by the presence of the intervening sulcus. This sulcus
is quite continuous with the posterior limiting sulcus of the insula, and
when followed round the temporal pole it is seen to lie directly in the
line of the depression, along the bottom of which the collateral fissure
is afterwards developed. Later on it may become a distinct and sharply-
cut fissure, the incisura temporalis of Schwalbe. Coincident with this
change the inner of the two polar gyri, which is continuous with the
hinder part of the insula, decreases in size and prominence until in
the eighth month it becomes more or less completely incorporated with
the uncus.

The inferior limiting sulcus of the insula, the incisura temporalis
which bounds the extremity of the uncus on its outer side, and the collateral
fissure lie therefore all in the same line, and may be regarded as the
bounding fissures of the temporal lobe. The inferior limiting sulcus of the
insula marks it off from the island of Reil; while the incisura temporalis and
the collateral fissure intervene between it and the great limbic lobe. But
further the growth forward of the extremity of the temporal pole is merely
a growth of the anterior part of the temporal operculum which, as we have
seen, first shows as the outermost of the two primitive polar gyri. It
extends forwards to meet the orbital operculum, and finally comes to
overlap it to a very considerable extent. There is no part of the opercular
arrangement which ultimately attains so great a depth.

Using the term " temporal pole," therefore, in its more restricted sense
(that is to say excluding the extremity of the uncus), it is important to
note that this part of the temporal lobe owes its existence to the forward
growth of the operculum.