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214

Cunningham Memoirs.

It is not common, however, to find a specimen of this variety of the intra-
parietal sulcus so characteristic as that represented in figure 41. Nevertheless
, of the 127 hemispheres examined, 17 came within the same class. In
all of these there was a long- continuous furrow placed behind the ascending
parietal convolution, and parallel with the fissure of Rolando. As a rule,
the upper part of this sulcus was shallower than the lower part, and in many
cases it was partially cut off from it by a deeply-placed bridging gyrus,
which crossed the bottom of the furrow and connected the posterior parietal
lobule with the ascending parietal convolution. Further, the superficial
bridge which intervened between the horizontal ramus of the fissure and the
vertical part was not so strongly marked. In the atlas accompanying
Grratiolet's Memoire sur les plis cerebraux de Vhomme this variety of the intraparietal
sulcus is exhibited in a very complete form in the left hemisphere
of the well-known " Hottentot Venus."

The following are the percentages for this variety of the intraparietal
sulcus in the different groups of cerebral hemispheres examined:—

63 Adult hemispheres,......11*1 per cent.

8 Negro hemispheres, ...... 25 ,,

19 Children's hemispheres, . . . . . 5*2

17 Full-time fcetal hemispheres, . . . . 11*7 „

20 Eighth-month fcetal hemispheres, . . . 25 ,,

Sernoff's results are again somewhat different from those which I have
obtained.

Variety IV.—The three farts of the sulcus confluent (fig. 42).—This is by
far the most usual condition of the intraparietal sulcus in the human brain.
It was present in sixty-nine of the cerebral hemispheres examined.

63 Adult hemispheres,......60*3 per cent.

8 Negro hemispheres, ...... 37"5 ,,

19 Children's hemispheres, ..... 57*8

17 Full-time foetal hemispheres, . . . . 41-3 ,,

20 Eighth-month fcetal hemispheres, . . . 50 ,,