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260

Cunningham Memoirs.

the case of the prsecentral sulcus the union is brought about either by an
upward rotation of the horizontal limb of the inferior sulcus, or by the
introduction of a new element which acts as a connecting link between the
two parts of the furrow.

Fia. 58.—Figure from Sernoff's work, reproduced by permission. It shows a continuous prsecentral

sulcus, produced by a blending of its several elements.

V. Sulcus Frontalis Secundus.—A very essential point to observe in
connexion with the inferior frontal sulcus is that its hinder end is placed
below the horizontal part of the inferior prsecentral sulcus (fig. 53, /.2,
p. 248). From this it proceeds forwards until it reaches a point immediately
above the ascending limb of the Sylvian fissure. Here it turns
slightly downwards, and ends by bifurcating into two branches, which
spread out widely from each other and form a terminal transverse piece
for the furrow. The lower of the two branches resulting from this
bifurcation cuts into the pars triangularis of the inferior frontal convolution
between the two anterior limbs of the Sylvian fissure (fig. 53).
If the lips of the inferior frontal sulcus be widely separated from
each other, it is seen to possess a considerable depth, whilst its walls
interlock with each other through the presence of alternating gyral
eminences. In some cases also, as Eberstaller has pointed out, it may be
partially interrupted by one or two deep annectant gyri. One of these
occurs midway between the two extremities of the furrow, whilst the other