Freiburger historische Bestände - digital

40

Cunningham Memoirs.

present in fig. 18 is represented. The manner in which it is produced is
evident. The gyrus cunei is on the surface ; and the hinder end of the stem
is prolonged upward between the gyrus cunei and the concealed gyrus
cuneo-lingualis anterior for a considerable distance into the cuneate lobe.
In this position it is apt at first sight to be mistaken for the parietooccipital
fissure.

Fig. 18. Fig. 19. Fig. 20.

S., "stem"; P.O., parieto-occipital; C, fore-part of posterior calcarine; C", hinder-part of
posterior calearine ; c., gyrus cunei; i.e., gyrus inter-cuneatus ; a.1., anterior cuneo-lingual
gyrus ; p.I., posterior cuneo-lingual gyrus.

In only one hemisphere was the arrangement represented in fig. 19
exhibited. Here the parieto-occipital fissure is broken into two by the elevation
of the intercuneate gyrus to the surface (i. <?.), and the anterior cuneo-
lingual gyrus is absent. In front of the parieto-occipital we note a shallow
furrow parallel to it. In cases in which this furrow deviates decidedly
from the normal type there appears to be a tendency for it to become double.
This is not the only case of doubling of the parieto-occipital fissure which
I have seen.

Fig. 20 exhibits a very interesting arrangement—a persistence, as
we shall afterwards see, of a foetal condition—in which the two parts of
the posterior calcarine fissure are completely cut off from each other as
well as from the " stem." The tsem also is carried up between the
cuneate and anterior cuneo-lingual gyri for a considerable distance into
the cuneate lobe.

A very essential point which must now be decided is the relation which
this system of fissures bears to the calcar avis or hippocampus minor of