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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 39

A somewhat important combination of the different parts of the
parieto-occipital and calcarine fissures is that in which the anterior
cuneo-lingual gyrus is absent, and the gyrus cunei and posterior
cuneo-lingual gyrus present (fig. 16). This was seen in ten hemispheres,
or in 7'8 per cent. In six of these the posterior cuneo-lingual gyrus
was concealed within the calcarine fissure; in four it was on the
surface.

A condition exactly the opposite of the foregoing is that in which the
cuneate gyrus is absent, and a direct continuity thus established between

s., .

P.O.,

c, .

c.", .

c, .
a.I., .
p.I., .

"stem," or anterior calcarine
fissure.

parieto-occipital fissure.

fore-part of the posterior calcarine
fissure.

hinder part of the posterior calcarine
fissure.

gyrus cunei.

gyrus cuneo-lingualis anterior,
gyrus cuneo-lingualis posterior.

Fig. 16.

Fig. 17.

the "stem" and the parieto-occipital fissure. In this case the two calcarine
annectant gyri are present (fig. 17). This occurred in four hemispheres,
or in 3-1 per cent.

Several other combinations of the parts concerned in this fissural
system were observed ; but as the conditions under which they are brought
about have been referred to, and as they occur very seldom we need not
enter into detail in regard to them. Three very unusual arrangements of
the fissures, however, must be specially noticed, inasmuch as they bear
directly upon certain points which we shall be dealing with when we
come to speak of the development of the parieto-occipital and calcarine
hssures. The accompanying diagrams will serve to make the conditions
met with in these cases apparent.

In the 127 hemispheres examined I met four in which the condition