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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 65

cranial wall in several children, and in all of them it was in front of the
lambda. The distance varied from one-third of an inch to one inch.

The cranial relations of the parieto-occipital fissure in the ape are also
of interest; and I subjoin a Table in which these are brought out by indices
obtained in a manner similar to those already given for the human head.
In PI. viii., also, drawings of the cerebrum in a macaque, baboon, cebus,
orang, and chimpanzee, exposed in situ, are given.

Lambdo-parieto-occipital Index in the Ape.

Mesial length of the Cerebrum, 100. The indices in evert/ case indicate relative distance in

front of the Lambda.

Kind of Ape.

No. of specimens
examined.

Index.

Chimpanzee, .....

2

5-5

Orang, ......

1

0 *

Cynocephalus, ....

1

8

Hamadryas, .....

1

13-2

Macaque, .....

2

20-4

Cebus,

2

18-5

In one chimpanzee the fissure coincided exactly with the lambda ; in the
other it was 11 mm. in front of this point. The average index for the two
was 5 *5 in front of the lambda. In the orang the fissure and the lambda
corresponded precisely with each other. Fer^f has given us the results he
has obtained on this matter in the heads of two young orangs. In both
cases the fissure was behind the lambda—in one 7 mm. and in the other
5 mm. In the determination of this point he employed the French
method of introducing pegs into the cerebrum through holes drilled in the
cranial wall, and then removing the brain. To say the least of it, this is

* Fissure coincides with lambda.

f "Contribution a 1'etude de la topographie cranio-cerebrale chez quelques singes," Journ.
Anat. et Phys., vol. xviii.

KOTAL IRISH ACADEMY.-CUNNINGHAM MEMOIRS, NO. VII, [9]