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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 125

In the early periods of growth and in the female the " Sylvian Point"
in the human brain is therefore placed slightly further back than in the
case of the adult and the male. In this respect the female exhibits the
retention of an infantile character, and shows a slight approach to the
condition present in the ape.

X. The length of the posterior horizontal limb of the Sylvian Fissure
.—Eberstaller of Grraz is the only anatomist who has sought to determine
with any degree of care the average length of the posterior horizontal
limb of the Sylvian fissure. It is somewhat difficult to fix upon two points
which can be accurately determined on every hemisphere between which
the measurements may be made. Posteriorly the fissure almost invariably
ends by bending suddenly upwards into the parietal lobe, and in many
cases it likewise sends downwards from the same point a short descending
branch. These terminal pieces have been distinguished as the ramus posterior
ascendens and the ramus posterior descendens. Eberstaller, in his
measurements, assumed as the posterior end of the fissure the angle which
the ramus posterior ascendens forms with the main stem. In those cases
where this point was not sufficiently well-marked, he called to his aid the
ramus posterior descendens, and by a study of both he fixed the posterior
end of the fissure. In front he selected the point of junction between the
ramus horizontalis anterior and the ramus horizontalis posterior or in cases
where there was only one anterior limb the point of union between this
and the posterior limb.

Eberstaller conducted his measurements with very great care, and with
every precaution towards the acquisition of reliable results. The fresh
cerebrum was extracted from the cranial cavity by cutting through the
mesencephalon. By a mesial incision the two hemispheres were set free,
and immersed in a water-bath, so that the natural configuration might be as
far as possible retained. The membranes were removed, and the measurements
made by means of a pair of compasses.

The first results which Eberstaller* published on this question were

* Zur Oberflachen-Anatomie der Grosshim-Hemispharen.—Vorlaufige Mittheilung.—Das
uutere Scheitellappchen.—Wiener Medizinisclie Blatter, No. 21. 1884.