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Dk. Cunningham—Surface Anatomy of the Primate Cerebrum. 227

cerebrum of another chimpanzee is given. On the left side the terminal
bifurcation of the intraparietal sulcus is exhibited, although it will be seen
that the lower limb is very weakly developed ; on the right side, however,
the intraparietal sulcus runs bodily into the bottom of the " Affenspalte."

I think we may fairly take the condition present in the chimpanzee
hemisphere figured in p. 226, as being the typical arrangement in this
animal, seeing that in two of the other three chimpanzee hemispheres
examined it was also present, although not in so marked a manner. Such
being the case if we now suppose the operculum abolished, and the two
annectant gyri in relation to the hinder end of the intraparietal sulcus
raised to the surface, we have the condition present in man. The terminal
bifurcation of the intraparietal sulcus, with its widely spread out limbs,
constitutes the sulcus trans versus. Instead of being completely or partially
concealed, as in the lower forms, it is in man exposed to view on the surface.

It is somewhat curious that we should obtain confirmatory evidence of
the accuracy of these views in an aberrant arrangement of the intraparietal
sulcus which was present in one of the specimens obtained from Cehus
albifrons. The cerebrum in question is figured in page 223. The left hemisphere
shows a condition closely corresponding to that observed in man.
Here the operculum is absent although the " Affenspalte" (a.f.) exists in
the shape of a curved fissure placed a short distance behind the parietooccipital
fissure. In this particular hemisphere the first annectant gyrus,
which in this species of ape is, as a rule, either absent or very feeble and
deeply placed (vide right hemisphere of same brain), is raised completely to
the surface (a.n.), and completely shuts off the parieto-occipital fissure from
the intraparietal sulcus. The ramus occipitalis of the intraparietal sulcus
is clearly marked out. It surrounds the first annectant gyrus externally,
and ends in a terminal bifurcation, the diverging limbs of which form a
sulcus occipitalis transversus (s. t) in every respect similar to the fissure
of the same name in the human brain.

At this stage I am induced to bring forward the cerebrum of a newly-
born child in which there is a fissure which is undoubtedly the representative
of the " Affenspalte " (fig. 49, p. 228). In front of this is seen the terminal
bifurcation of the occipital part of the intraparietal sulcus forming the

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