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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 193

11. The relative position of the fissure of Rolando, on the surface of
the cerebrum, is the same in the two sexes, and also in the two hemispheres.

12. The parietal bone, and the area of brain immediately subjacent, do
not grow at an equal pace. In the early stages of its development the
fissure of Rolando lies close to the coronal suture, but this does not mean
that it lies far forward on the brain, but simply, that the parietal bone forms,
at a later stage, a relatively greater extent of the cranial vault.

13. The position of the fissure on the surface of the cerebrum is more
fixed than the position of the coronal suture on the cranial vault at different
periods of growth.

14. In the anthropoid apes the upper end of the fissure of Rolando is
placed relatively further back on the cerebrum than in man.

15. The average Rolandic angle in the human brain is 71°'7. There is
no sexual difference in this respect, but it would appear that in brachyce-
phalic heads the angle opens out, and in dolichocephalic heads it becomes
more acute.

16. The average relative length of the fissure of Rolando in the adult
human brain is 39*3. If there is any sexual distinction in this respect the
fissure is relatively longer in the female that in the male. In all probability
the variations in the relative length of the fissure are due to differences in
the shape of the head.

ROYAL IRISH ACADEMY.-CUNNINGHAM MEMOIRS. NO. Til.

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