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Mr. Victor Horsley—Cranio-Cerebral Topography.

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ingenious and simple, nevertheless did not provide for sufficient accuracy.
In endeavouring to consider how an improvement might be effected, it
appeared clear that the solution lay in a true calculation of the angle which
the fissure makes anteriorly with the middle line. The researches of Meyer
had shown the effect of arrest of the cranial growth in determining a greater
or less degree of transversality in the direction of the cerebral fissures.
It was probable, therefore, that if the cephalic index were properly
determined, a distinct relationship would be shown to exist between it
and the Rolandic angle. For this purpose I made a number of measurements
, under the kind guidance and correction of Professor Cunningham,
of the invaluable material—viz. brains hardened in situ—in his laboratory,
since this question can at present alone be answered upon a basis of
such preparations.

In studying the literature of cerebral topography I was interested in
finding that the probable truth of this idea had been foreseen by the prescience
of Broca, as Foulhouze records that in a conversation with him he
had suggested that some sort of relationship of this kind would possibly be
found to exist. Moreover, that Riidinger had stated that the difference
in proportionate lengths of dolicho- and brachy-cephalic heads was particularly
due to growth of the mesial border of the parietal bone, so that the
ascending gyri in brachycephaly had a more transverse direction, and the
opposite in dolichocephaly; and that further, the upper end of the fissure
of Rolando was situated a greater distance behind the bregma in dolichocephaly
than in brach}Tcephaly. This last point all observers' measurements
quite confirm, except Le Fort. Further, that in the female the direction
of the parietal sulci made a smaller angle with the middle line than in the
male. Passet, working under Riidinger's direction, found, in brains
previously injected and measured in situ, that the average angle in males
was 60-9°, in females 64-2°. On the other hand, Professor Cunningham
has taken up the point, and, as may be seen on pp. 186 et seq.,
has come to the opinion that there is no sexual difference in the
angle of different individuals, that the average adult angle is 71-7°, and
that its degree rises and falls with the respective variations of the cephalic
index.

ROYAL IRISH ACADEMY.—CUXNIXGHAM MEMOIRS, IS'O. YET. [421