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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 149

do the same in the case of the ape-cerebrum. The following Table gives
the required data :—

Relative position of the Sylvian Fissure on the Surface of the Hemisphere

in different Apes.

Parieto-temporal Depth = 100.



Number of
Hemispheres
Examined.

Parietal
Depth.

Temporal
Depth.

Cebus (1 C. capucinus,

2 C. albifrons),

6

66-9

331

Baboon,



7

66-6

33-4

Macaque,



5

65-4

34-6

Hamadryas,



2

64-8

35-2

Orang,



2

71

29

Chimpanzee,



4

71-2

28-8

The indices presented in this Table by the low apes resemble those
obtained for the human child of four to five years old (65'7— 34-3), and this
being the case, we should naturally expect that the cranial relations of
these apes would show some similarity to those exhibited at the same period
of human growth. This is very far from being the case. Only in the
cebus is the Sylvian fissure placed above the squamous suture; in the
others the fore-part of the fissure is cither placed at a lower level than the
suture or coincides with the suture.

In the orang and the chimpanzee the parietal depth is relatively greater
than in the adult human cerebrum. This is very remarkable when we
consider that the orang examined was only six years old, whilst both chimpanzees
were little more than three years old.

In spite of this greater relative parietal depth in the orang, we find a
close resemblance between relations presented by the Sylvian fissure and
the squamous suture in this ape and the corresponding relations in the
adult human head. This is, no doubt, due to the fact that the squamous
bone in the orang does not reach to the same relative height as in the
cranium of man. It is both interesting and curious, therefore, to note that