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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 177

lower end, as might be expected from the fact that it is first formed, shows
the least change. As development and growth proceed it moves back
slightly, but only to an almost inappreciable extent. When it first appears
the lower fronto-Rolandic index is 41*8, but in a few weeks it soon establishes
its proper relations, and from this time on it fluctuates between 42-3
and 43*3. These fluctuations can hardly be regarded as indicating differences
of position at different periods of growth. If larger numbers of
brains were examined, I am satisfied that they would disappear altogether.

The upper end of the fissure of Rolando is not so fixed in its relations
at different periods of life. It will be seen that it is laid down very much
in the same relative position that it afterwards occupies in the adult.
Compare the indices 52*7 and 53'3. From this point the upper end of the
fissure moves backwards until it gains an index of 56*7. This new position
is apparently acquired very rapidly—in the course of about four or six
weeks—and it represents the climax of the backward movement. No
doubt it is produced by an accelerated growth of the upper part of the
frontal lobe during the period of the change. It is curious to note in the
succeeding month that a movement in the opposite direction takes place:
the upper end of the fissure travels slowly forward until the index becomes
55*2 in foetuses from 1\ to 8^ months, and finally 53'5 in the new-born
full-time child. At birth, then, the upper end of the fissure becomes fixed,
and remains so in after life. I do not lay any importance on the somewhat
low indices obtained for the brains of the children of eleven, twelve, and
fifteen years old. The number of hemispheres measured was too small to
allow us to base any generalization upon the results obtained from them.

Huschka, in his remarkable work entitled Schddel, Him und Seele, published
in 1854, contends that marked sexual differences can be detected in
the human cerebrum. He asserts that in the male a relatively greater mass
of the hemisphere lies in front of the fissure of Rolando, whilst in the
female a greater mass lies behind it. To use his own words :— " Das Weib
ist ein homo parietdlis und inter-parietalis, der Mann ein homo frontalis.''''
Rudinger* gives expression to somewhat similar views. He insists strongly

* Ueber die Unterschiede der Grossbmiwindungen nach dem Gescblecbt beim Foetus und
Neugeborenen. Muncben, 1877.

ROYAL IRISH ACADEMY.-CUNNINGHAM MEMOIRS, NO. VII. [231